Effect of dehydration and hyperosmolal hydration on lignocaine and metabolites disposition in conscious rabbits.

1. The present study aimed to investigate the effect of dehydration and hyperosmolal hydration on the disposition of lignocaine and two of its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX). 2. Lignocaine was infused to three groups of conscious rabbits: controls, rabbits previously deprived of water for 48 h and rabbits receiving an infusion of 2.5% NaCl. 3. In dehydrated and hyperosmolal-hydrated rabbits, plasma osmolality was 321 +/- 1 and 313 +/- 1 mOsm kg-1, respectively (P < 0.01 compared to controls, 285 +/- 1 mOsm kg-1). In dehydrated animals, baseline values of plasma arginine vasopressin (AVP) concentrations and plasma renin activity (PRA) were higher than in controls, i.e. 12.4 +/- 1.4 pg ml-1 and 15.4 +/- 1.7 ng AI ml-1 h-1 vs. 3.4 +/- 0.2 pg ml-1 (P < 0.01), and 5.1 +/- 0.6 ng AI ml-1 h-1 (P < 0.01), respectively; atrial natriuretic peptide (ANP) decreased from 55 +/- 11 to 32 +/- 4 pg ml-1 (P < 0.05). Compared to controls, hyperosmolal hydration only increased AVP to 15.5 +/- 0.7 pg ml-1 (P < 0.01). 4. Under both experimental conditions, lignocaine plasma concentrations were almost double (P < 0.01) those in controls, due to a lower systemic clearance, e.g. 54 +/- 3 and 59 +/- 1 vs. 96 +/- 5 ml min-1 kg-1, respectively. Plasma levels of MEGX increased (P < 0.01) only in dehydrated animals, although GX plasma concentrations were augmented (P < 0.01) about three fold in both groups of animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Grapefruit juice-felodipine interaction: reproducibility and characterization with the extended release drug formulation.

1. Felodipine 10 mg extended release was administered with 250 ml regular-strength grapefruit juice or water in a randomized crossover manner followed by a second grapefruit juice treatment in 12 healthy men. The pharmacokinetics of felodipine and primary oxidative metabolite, dehydrofelodipine, were evaluated. 2. Initial grapefruit juice treatment increased felodipine AUC (mean +/- s.d.; 56.6 +/- 21.9 vs 28.1 +/- 11.5 ng ml-1 h; P < 0.001) and Cmax (8.1 +/- 2.5 vs 3.3 +/- 1.2 ng ml-1; P < 0.001) compared with water. Felodipine tmax (median; 2.8 vs 3.0 h) and t1/2 (7.3 +/- 3.7 vs 6.9 +/- 3.6 h) were not altered. 3. Readministration of felodipine with grapefruit juice produced mean felodipine AUC (61.5 +/- 32.2 ng ml-1 h) and Cmax (8.4 +/- 4.8 ng ml-1) which were similar to the initial grapefruit juice treatment 1-3 weeks previously. Felodipine AUC (r = 0.73, P < 0.01) and Cmax (r = 0.69, P < 0.02) correlated between grapefruit juice treatments among individuals. 4. The % increase in felodipine AUC with the initial grapefruit juice treatment compared with water correlated with the % increase in felodipine Cmax among individuals (r = 0.80, P < 0.01). Dehydrofelodipine AUC (74.7 +/- 28.7 vs 48.5 +/- 16.3 ng ml-1 h; P < 0.01) and Cmax (12.1 +/- 2.9 vs 7.9 +/- 2.6 ng ml-1; P < 0.01) were augmented with grapefruit juice compared with water.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relative bioavailability of a new oral form of cyclosporin A in patients with rheumatoid arthritis.

The relative bioavailability of cyclosporin A (CsA) from a new microemulsion oral formulation (NEO) and the currently used soft gelatine capsule (SGC) was determined at steady state in 12 patients with rheumatoid arthritis. The AUC(0,12 h) values of cyclosporin A were significantly greater after NEO than SGC (2873 +/- 848 ng ml-1 h (mean +/- s.d.) vs 2355 +/- 1128 ng ml-1 h; P = 0.02, 95% CI (confidence interval of the difference: 81 to 955 ng ml-1 h). Cmax values were significantly higher after NEO than after SGC (811 +/- 244 ng ml-1 vs 495 +/- 291 ng ml-1, P < 0.0001, 95% CI of the difference: 209 to 422 ng ml-1).     

Characterization of tachykinin receptors mediating plasma extravasation and vasodilatation in normal and acutely inflamed knee joints of the rat.

1. Inflammatory actions of tachykinins in normal rat knee joints were compared with those of animals with acutely inflamed joints induced by intra-articular injection of 2% carrageenan. Plasma protein extravasation in rat knee joints, measured by protein micro-turbidimetry, was induced by intra-articular perfusion of selective tachykinin receptor agonists. Changes in joint blood flow, measured by laser Doppler perfusion imaging, were produced by topical applications of selective tachykinin receptor agonists to the joint capsule. 2. Carrageenan-injected rat knee joints showed significantly higher (P < 0.001) basal plasma extravasation (56 +/- 4 micrograms ml-1, n = 5) than normal rat knee joints (10 +/- 4 micrograms ml-1, n = 6). Intra-articular perfusion of the selective neurokinin1 (NK1) receptor agonist [Sar9, Met(O2)11]-substance P (0.8 nmol min-1) for 60 min elevated the basal plasma extravasation to 90 +/- 17 micrograms ml-1 (n = 6, P < 0.001) in normal joints, and to 150 +/- 14 micrograms ml-1 (n = 5, P < 0.001) in inflamed joints. Perfusion of the selective NK1 receptor antagonist N2-[(4R)-4-hydroxy-1-(1-methyl-1H- indol-3-yl)carbonyl-L-prolyl]-N-methyl-N-phenylmethyl-3-(2-naphthyl)- L-alaninamide (FK888; 0.8 nmol min-1) for 20 min followed by co-perfusion with the NK1 receptor agonist (0.8 nmol min-1) produced complete inhibition of the NK1 receptor agonist-induced plasma extravasation in the two groups of animals (for both groups; n = 3, P < 0.001). 3. Intra-articular perfusion of the selective NK receptor agonist [Nle10]-neurokinin A4-10 (0.8 nmol min-1) and the selective NK3 receptor agonist [MePhe7]-neurokinin B (0.8 nmol min1) produced no increase in plasma extravasation in normal or in inflamed rat knee joints (n = 4 and 11, P > 0.05). 4. Topical bolus applications of the NK1 receptor agonist [Sar9, Met(O2)11]-substance P onto normal joint capsules produced dose-dependent vasodilatation expressed as a voltage increase from control level. The maximum increase in blood flow was 2.05-0.21 V from a basal voltage of 3.42 +/- 0.07 V (n = 13, P < 0.001). To a much lesser extent, administration of the NK2 receptor agonist [Nle10]-neurokinin A4-10 also produced dose-dependent vasodilatation with maximum increase of 0.46 +/- 0.08 V from a basal level of 3.38 +/- 0.1 V (n = 7, P < 0.01). Animals with acutely inflamed joints showed enhanced vasodilator responses to the NK1 and NK2 receptor agonists (for both: P vs non-inflamed joints < 0.001). Thus, the NK1 and NK2 receptor agonists produced maximum increases of 2.56 +/- 0.19 V (basal level = 5.84 +/- 0.07 V; n = 7, P < 0.001) and 1.97 +/- 0.26 V (basal level = 6.31 +/- 0.23 V; n = 11, P < 0.001), respectively. The NK3 receptor agonist [MePhe7]-neurokinin B produced no change in blood flow in normal or in inflamed rat knee joints (n = 7 and 5, P > 0.05). 5. Bolus administration of the NK1 receptor antagonist FK888 (10 pmol) alone followed 5 min later by another dose of 10 pmol FK888 (i.e. total dose of 2 x 10 pmol) applied together with the NK1 receptor selective agonist [Sar9, Met(O2)11]-substance P produced partial, but significant inhibition of the NK1 receptor agonist-induced vasodilatation in both normal (maximum response reduced by 51.9 +/- 5.4%; n = 6, P < 0.001) and inflamed rat knee joints (maximum response reduced by 49.3 +/- 6.1%; n = 5, P < 0.001). The NK2 receptor agonist [Nle10]-neurokinin A4-10-induced vasodilator responses in inflamed joints were not affected by this treatment (n = 6, P > 0.05). However, with two higher doses of FK888 (both 1 nmol), the NK1 and the NK2 receptor agonist-induced vasodilator responses were abolished in the two groups of animals (n = 6-8, P < 0.005). 6. Administration of two doses of the selective NK2 receptor antagonist (S)-N-methyl-N-[4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) -butyl]benzamide (SR48968;...     

The influence of gender and sex steroid hormones on the plasma binding of propranolol enantiomers.

1. Plasma binding of tritium-labelled racemic propranolol (P) was measured by equilibrium dialysis. The unbound enantiomers were separated by h.p.l.c. after chiral derivatization. The binding of (-)-P was higher than that of (+)-P. 2. Contrary to previous suggestions, a sex difference in the plasma binding of the P enantiomers (9 young women, 12 young men) was not observed. The unbound percentage of (-)-P was 9.2 +/- 1.8 (mean +/- s.d.) in women vs 9.1 +/- 1.7 in men; for (+)-P it was 10.8 +/- 1.8 vs 10.8 +/- 2.1. 3. In the nine women, the binding did not change with fluctuating plasma oestradiol concentrations during the menstrual cycle. Testosterone cypionate doubled the circulating concentrations of testosterone in eight men but had no effect on P binding. 4. Ethinyl oestradiol (50 micrograms day-1) alone or together with norethindrone (OCD) in eight of the women produced an increase in the unbound percentage of both (-)-P (11.4 +/- 2.6 vs 9.5 +/- 1.6 for control; P < 0.001) and (+)-P (13.2 +/- 2.5 vs 11.2 +/- 1.5 for control; P < 0.001). This was due to a decrease in the plasma concentrations of alpha 1-acid glycoprotein from 0.54 +/- 0.11 mg ml-1 in control to 0.37 +/- 0.08 mg ml-1 (P < 0.001) during ethinyl oestradiol treatment. 5. Enantioselectivity in the unbound fraction of P increased with increasing total binding from a (-)/(+)-ratio of 0.93 at 84% binding to a (-)/(+)-ratio of 0.78 at 94% binding (P < 0.001).     

Contribution of the renin-angiotensin system to short-term blood pressure variability during blockade of nitric oxide synthesis in the rat.

1. The aim of this study was to investigate, by use of spectral analysis, (1) the blood pressure (BP) variability changes in the conscious rat during blockade of nitric oxide (NO) synthesis by the L-arginine analogue NG-nitro-L-arginine methyl ester (L-NAME); (2) the involvement of the renin-angiotensin system in these modifications, by use of the angiotensin II AT1-receptor antagonist losartan. 2. Blockade of NO synthesis was achieved by infusion for 1 h of a low-dose (10 micrograms kg-1 min-1, i.v., n = 10) and high-dose (100 micrograms kg-1 min-1, i.v., n = 10) of L-NAME. The same treatment was applied in two further groups (2 x n = 10) after a bolus dose of losartan (10 mg kg-1, i.v.). 3. Thirty minutes after the start of the infusion of low-dose L-NAME, systolic BP (SBP) increased (+10 +/- 3 mmHg, P < 0.01), with the effect being more pronounced 5 min after the end of L-NAME administration (+20 +/- 4 mmHg, P < 0.001). With high-dose L-NAME, SBP increased immediately (5 min: +8 +/- 2 mmHg, P < 0.05) and reached a maximum after 40 min (+53 +/- 4 mmHg, P < 0.001); a bradycardia was observed (60 min: -44 +/- 13 beats min-1, P < 0.01). 4. Low-dose L-NAME increased the low-frequency component (LF: 0.02-0.2 Hz) of SBP variability (50 min: 6.7 +/- 1.7 mmHg2 vs 3.4 +/- 0.5 mmHg2, P < 0.05), whereas the high dose of L-NAME not only increased the LF component (40 min: 11.7 +/- 2 mmHg2 vs 2.7 +/- 0.5 mmHg2, P < 0.001) but also decreased the mind frequency (MF: 0.2-0.6 Hz) component (60 min: 1.14 +/- 0.3 mmHg2 vs 1.7 +/- 0.1 mmHg2, P < 0.05) of SBP. 5. Losartan did not modify BP levels but had a tachycardic effect (+45 beats min-1). Moreover, losartan increased MF oscillations of SBP (4.26 +/- 0.49 mmHg2 vs 2.43 +/- 0.25 mmHg2, P < 0.001), prevented the BP rise provoked by the low-dose of L-NAME and delayed the BP rise provoked by the high-dose of L-NAME. Losartan also prevented the amplification of the LF oscillations of SBP induced by L-NAME; the decrease of the MF oscillations of SBP induced by L-NAME was reinforced after losartan. 6. We conclude that the renin-angiotensin system is involved in the increase in variability of SBP in the LF range which resulted from the withdrawal of the vasodilating influence of NO. We propose that NO may counterbalance LF oscillations provoked by the activity of the renin-angiotensin system.     

Effect of dexamethasone and endogenous corticosterone on airway hyperresponsiveness and eosinophilia in the mouse.

1. Mice were sensitized by 7 intraperitoneal injections of ovalbumin without adjuvant (10 micrograms in 0.5 ml of sterile saline) on alternate days and after 3 weeks exposed to either ovalbumin (2 mg ml-1 in sterile saline) or saline aerosol for 5 min on 8 consecutive days. One day before the first challenge, animals were injected intraperitoneally on a daily basis with vehicle (0.25 ml sterile saline), dexamethasone (0.5 mg kg-1) or metyrapone (30 mg kg-1). 2. In vehicle-treated ovalbumin-sensitized animals ovalbumin challenge induced a significant increase of airway responsiveness to metacholine both in vitro (27%, P < 0.05) and in vivo (40%, P < 0.05) compared to saline-challenged mice. Virtually no eosinophils could be detected after saline challenge, whereas the numbers of eosinophils were significantly increased (P < 0.01) at both 3 and 24 h after the last ovalbumin challenge (5.48 +/- 3.8 x 10(3) and 9.13 +/- 1.7 x 10(3) cells, respectively). Furthermore, a significant increase in ovalbumin-specific immunoglobulin E level (583 +/- 103 units ml-1, P < 0.05) was observed after ovalbumin challenge compared to saline challenge (201 +/- 38 units ml-1). 3. Plasma corticosterone level was significantly reduced (-92%, P < 0.001) after treatment with metyrapone. Treatment with metyrapone significantly increased eosinophil infiltration (17.4 +/- 9.93 x 10(3) and 18.7 +/- 2.57 x 10(3) cells, P < 0.05 at 3 h and 24 h, respectively) and potentiated airway hyperresponsiveness to methacholine compared to vehicle-treated ovalbumin-challenged animals. Dexamethasone inhibited both in vitro and in vivo hyperresponsiveness as well as antigen-induced infiltration of eosinophils (0, P < 0.05 and 0.7 +/- 0.33 x 10(3) cells, P < 0.05 at 3 h and 24 h, respectively). Metyrapone as well as dexamethasone did not affect the increase in ovalbumin-specific immunoglobulin E levels after ovalbumin challenge (565 +/- 70 units/ml-1; P < 0.05; 552 +/- 48 units ml-1, P < 0.05 respectively). 4. From these data it can be concluded that exogenously applied corticosteroids can inhibit eosinophil infiltration as well as airway hyperresponsiveness. Vise versa, endogenously produced corticosteroids play a down-regulating role on the induction of both eosinophil infiltration and airway hyperresponsiveness.     

Dose of midazolam should be reduced during diltiazem and verapamil treatments.

1. The effects of diltiazem and verapamil on the pharmacokinetics and pharmacodynamics of midazolam were investigated in a double-blind randomized cross-over study of three phases. 2. Nine healthy volunteers were given orally diltiazem (60 mg), verapamil (80 mg) or placebo three times daily for 2 days. On the second day they received a 15 mg oral dose of midazolam, after which plasma samples were collected and performance tests carried out for 17 h. 3. The area under the midazolam concentration-time curve was increased from 12 +/- 1 microgram ml-1 min to 45 +/- 5 micrograms ml-1 min by diltiazem (P < 0.001) and to 35 +/- 5 micrograms ml-1 min by verapamil (P < 0.001). The peak midazolam concentration was doubled (P < 0.01) and the elimination half-life of midazolam prolonged (P < 0.05) by both diltiazem and verapamil treatments. 4. These changes in the pharmacokinetics of midazolam were also associated with profound and prolonged sedative effects. 5. If the administration of midazolam cannot be avoided, the dose of midazolam should be reduced during concomitant treatment with diltiazem and verapamil.     

Pharmacokinetics of the enantiomers of bupivacaine following intravenous administration of the racemate.

1. The pharmacokinetics of R(+)-bupivacaine and S(-)-bupivacaine were investigated following a 10 min intravenous infusion of the racemate (dose 30 mg) in 10 healthy males. 2. The fractions unbound of R(+)- and S(-)-bupivacaine in pre-dose plasma were determined for each subject after in vitro addition of rac-bupivacaine (concentration of each enantiomer: approximately 300 ng ml-1). 3. The total plasma clearance of R(+)-bupivacaine (mean +/- s.d.: 0.395 +/- 0.076 l min-1) was greater (P < 0.0001) than that of S(-)-bupivacaine (0.317 +/- 0.067 l min-1). The volumes of distribution of R(+)-bupivacaine at steady state (84 +/- 29 l) and during the terminal log-linear phase (117 +/- 47 l) were larger (P < 0.0002) than those of S(-)-bupivacaine (54 +/- 20 l and 71 +/- 34 l, respectively). The terminal half-life (210 +/- 95 min) and mean residence time (215 +/- 74 min) of R(+)-bupivacaine were longer than those of S(-)-bupivacaine (157 +/- 77 min, P < 0.01, and 172 +/- 55 min, P < 0.02, respectively). 4. The free percentage of R(+)-bupivacaine (6.6 +/- 3.0 %) was greater (P < 0.0002) than that of S(-)-bupivacaine (4.5 +/- 2.1 %). 5. The plasma clearance of unbound R(+)-bupivacaine (7.26 +/- 3.60 1 min-1) was smaller (P < 0.01) than that of S(-)-bupivacaine (8.71 +/- 4.27 l min-1). Volumes of distribution based on unbound R(+)-bupivacaine concentrations (Vuss: 1576 +/- 934 l; Vu: 2233 +/- 1442 l) did not differ from those of S(-)-bupivacaine (Vuss: 1498 +/- 892 l; Vu: 1978 +/- 1302 l). 6. The enantioselective systemic disposition of bupivacaine can to a large extent be attributed to differences in the degree of plasma binding of the enantiomers.     

The influence of renal function on the enantioselective pharmacokinetics and pharmacodynamics of ketoprofen in patients with rheumatoid arthritis.

1. Single oral doses of 100 mg racemic ketoprofen were given to 15 patients (age range: 51-79 years) with rheumatoid arthritis and a range of creatinine clearances (CLCR) from 26 to 159 ml min-1. 2. The fractions unbound of (R)- and (S)-ketoprofen in plasma were determined for each subject after in vitro addition of rac-ketoprofen (enantiomer range: 1.00-6.00 micrograms ml-1) to pre-dose plasma. 3. An index of the antiplatelet effect of ketoprofen in vitro was measured as inhibition of platelet thromboxane B2 (TXB2) generation during the controlled clotting of whole blood (pre-dose) spiked with rac-ketoprofen. 4. In vivo studies revealed significant associations (P < 0.05) between the reciprocal of AUC for both unbound and total (bound plus unbound) (S)-ketoprofen and CLCR. Corresponding relationships were also observed for the (R)-enantiomer of ketoprofen. In addition, the half-life of each enantiomer was negatively correlated with CLCR. There was a positive relationship between the 24 h urinary recovery of combined non-conjugated and conjugated (R)-ketoprofen and CLCR while that for the (S)-stereoisomer failed to reach statistical significance (P > 0.05). 5. There was no difference between AUC for (R)- and (S)-ketoprofen for either unbound or total drug. 6. The mean +/- s.d. percentage unbound of (S)-ketoprofen in plasma (0.801 +/- 0.194%) exceeded (P < 0.05) the corresponding value for its optical antipode (0.724 +/- 0.149%). The percentage unbound of the (S)-enantiomer was higher at 6.00 micrograms ml-1 than that at enantiomer concentrations of 3.50 micrograms ml-1 and below, where it was invariant. The percentage unbound of (R)-ketoprofen was independent of plasma concentration up to 6.00 micrograms ml-1. There were no correlations between the percentage unbound of each enantiomer and either serum albumin concentration or CLCR. 7. The relationship between the serum concentration of unbound (S)-ketoprofen and the percentage inhibition of platelet TXB2 generation was described by a sigmoidal Emax equation for each patient. There was no correlation between the unbound concentration of (S)-ketoprofen in serum required to inhibit platelet TXB2 generation by 50% (EC50) and CLCR. The mean +/- s.d. EC50 was 0.216 +/- 0.143 ng ml-1. 8. These data indicate that diminished renal function is associated with an increased exposure to unbound (S)-ketoprofen, presumably due to regeneration of parent aglycone arising from the hydrolysis of accumulated acyl-glucuronide conjugates. The apparent sensitivity of platelet cyclo-oxygenase to the inhibitory effect of (S)-ketoprofen was not influenced by renal function.     

Metabolic disposition of proguanil in extensive and poor metabolisers of S-mephenytoin 4'-hydroxylation recruited from an Indonesian population.

1. The metabolism of proguanil (PG) was studied by measuring PG, cycloguanil (CG) and 4-chlorophenylbiguanide (CPB) in plasma and urine samples after an oral 200 mg dose of PG hydrochloride administered to 14 extensive (EMs) and 10 poor hydroxylators (PMs) of S-mephenytoin of Indonesian origin. 2. The mean ( +/- s.d.) values of the elimination half-life (t 1/2) and AUC of PG were significantly (P < 0.01) greater in the PM than in the EM group (20.6 +/- 3.1 vs 14.6 +/- 3.5 (95% confidence intervals of difference 3.1 to 8.9) h; and 5.43 +/- 1.89 vs 3.68 +/- 0.83 (0.58 to 2.91) micrograms ml-1 h). 3. Plasma concentrations of CG, an active metabolite, could not be detected in all PMs, and those of CPB were sufficiently high to determine a time-course in only four PMs. Mean AUC(0,24 h) values of CPB were significantly (P < 0.05) lower in the PM (n = 4) than in the EM group (n = 14) (0.47 +/- 0.13 vs 0.88 +/- 0.50 (-0.14 to 0.96) micrograms ml-1 h). 4. Log10 percentage urinary recovery of 4'-hydroxymephenytoin correlated significantly (P < 0.05) with the t 1/2 (rs = -0.661) and AUC (rs = -0.652) of PG. 5. PG, CG and CPB were detectable in urine at 12 h in all subjects. Log10 percentage urinary recovery of 4'-hydroxymephenytoin correlated significantly (P < 0.01) with urinary PG/CG (rs = -0.876), PG/CPB (rs = -0.833) and PG/(CG + CPB) (rs = -0.831) metabolic ratios.(ABSTRACT TRUNCATED AT 250 WORDS)     

The potentiation of adrenaline-induced in vitro platelet aggregation by ADP, collagen and serotonin and its inhibition by naftopidil and doxazosin in normal human subjects.

1. Aggregation in platelet-rich plasma from normotensive men was induced by adrenaline (0.25-16 microM), ADP (0.25-16 microM), collagen (0.25-8 micrograms ml-1) or serotonin (10 microM) alone, or by previously sub-threshold concentrations of adrenaline (0.03-1 microM) in combination with sub-threshold concentrations of serotonin (2.5 microM), ADP (0.5 microM) or collagen (0.125 micrograms ml-1). The effects of the alpha 1-adrenoceptor blockers naftopidil and doxazosin on platelet aggregation were investigated. 2. The dose-response curves for collagen and ADP were unaffected by either drug. However, naftopidil (40 microM) inhibited serotonin-induced platelet aggregation (23.9%, 95% confidence interval (CI) 10.7 to 37.1%; P < 0.01) and caused a slight shift to the right of the adrenaline dose-response curve with a mean increase in the EC50 value of 0.5 microM (95% CI 0.07 to 0.93 microM; P < 0.05). Doxazosin had no effect on serotonin or adrenaline-induced aggregation. 3. A marked potentiation of the aggregation induced by subthreshold concentrations of adrenaline resulted from the prior addition of low concentrations of ADP, collagen or serotonin. 4. These potentiated responses were inhibited in a dose-dependent manner by naftopidil and to a lesser extent doxazosin. The maximum inhibitions (%) produced by naftopidil (40 microM) on the responses of adrenaline potentiated by ADP were 58.3% (95% CI 36.8 to 79.8%; P < 0.001), serotonin 58.9% (95% CI 40.0 to 77.8%; P < 0.001), and collagen 70.9% (95% CI 52.5 to 89.3%; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Drug-induced in vitro inhibition of neutrophil-endothelial cell adhesion.

1. Leukocyte-endothelial cell interactions play an important role during ischaemia-reperfusion events. Adhesion molecules are specifically implicated in this interaction process. 2. Since defibrotide has been shown to be an efficient drug in reducing damage due to ischaemia-reperfusion in many experimental models, we analysed the effect of defibrotide in vitro on leukocyte adhesion to endothelial cells in basal conditions and after their stimulation. 3. In basal conditions, defibrotide (1000 micrograms ml-1) partially inhibited leukocyte adhesion to endothelial cells by 17.3% +/- 3.6 (P < 0.05), and after endothelial cell stimulation (TNF-alpha, 500 u ml-1) or after leukocyte stimulation (fMLP, 10(-7) M), it inhibited leukocyte adhesion by 26.5% +/- 3.4 and 32.4% +/- 1.8, respectively (P < 0.05). 4. In adhesion blockage experiments, the use of the monoclonal antibody anti-CD31 (5 micrograms ml-1) did not demonstrate a significant inhibitory effect whereas use of the monoclonal antibody anti-LFA-1 (5 micrograms ml-1) significantly interfered with the effect of defibrotide. 5. This result was confirmed in NIH/3T3-ICAM-1 transfected cells. 6. We conclude that defibrotide is able to interfere with leukocyte adhesion to endothelial cells mainly in activated conditions and that the ICAM-1/LFA-1 adhesion system is involved in the defibrotide mechanism of action.     

Inhibition of substance P-induced microvascular leakage by inhaled methoxamine in rat airways.

1. The effect of the inhaled alpha-adrenoceptor agonist, methoxamine (MTX), was studied on experimental airway oedema induced by injection of substance P (SP) in the rat. Sprague-Dawley rats (300-350 g) were anaesthetized with sodium thiopentone, tracheotomized and artificially ventilated. 2. MTX or its vehicle was administered by inhalation. Airway resistance and blood pressure were monitored continuously. Evans Blue dye (EB, 20 mg kg-1) was injected through a jugular catheter 1 min before SP (14.8 nmol kg-1). Airways were dissected out, weighed and placed in formamide for EB extraction and determination by spectrophotometry. 3. EB extravasation induced by SP was significantly reduced in distal intraparenchymal bronchi by inhaled MTX at doses of 50 micrograms kg-1 (58 +/- 9 vs 96 +/- 9 ng EB mg-1 tissue after vehicle, P < 0.001) and 100 micrograms kg-1 (69 +/- 11 vs 137 +/- 26 ng EB mg-1 tissue after vehicle, P < 0.01). Inhaled MTX by itself (100 micrograms kg-1) increased blood pressure: 172 +/- 6 vs 132 +/- 10 mmHg baseline (P < 0.02), but neither induced extravasation nor increased airway resistance. 4. In another set of experiments without SP, MTX was administered intravenously 1 min after EB. At 100 micrograms kg-1, i.v. MTX increased blood pressure to a similar extent as inhaled MTX (180 vs 147 mmHg baseline, P < 0.01), increased airway resistance and caused leakage of plasma proteins in distal intraparenchymal bronchi (79 +/- 7 vs 47 +/- 1 ng EB mg-1 tissue, P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Modulation by atrial natriuretic factor of receptor-mediated cyclic AMP-dependent responses in canine pulmonary artery during heart failure.

1. Pacing-induced congestive heart failure (CHF) in dogs is associated with increased plasma levels of atrial natriuretic factor (ANF) and inhibition of receptor-mediated cyclic AMP-dependent relaxation in isolated pulmonary arteries (PA). Since ANF is known to be negatively coupled to adenylate cyclase, we studied cyclic AMP-mediated relaxation to isoprenaline (Iso) and arachidonic acid (AA) in PA from control dogs (C), dogs with pacing-induced CHF (CHF) and dogs with bilateral atrial appendectomy and CHF (ATR APP+CHF). 2. In CHF, plasma ANF levels increased from a baseline of 80 +/- 8 pg ml-1 to 283 +/- 64 pg ml-1 (P < 0.05), but the ATR APP+CHF group failed to show this increase (67 +/- 7 pg ml-1 vs 94 +/- 15 pg ml-1, P = NS). Plasma ANF levels, however, did not influence myocardial dysfunction in CHF. 3. The relaxation of 49 +/- 5% to 1 microM Iso in C was reduced to 23 +/- 4% in CHF (P < 0.05), but relaxation of 49 +/- 12% was observed in the ATR APP+CHF group (P = NS vs C). Relaxation responses to 10 microM AA were as follows: 77 +/- 5% (C, n = 8), 27 +/- 8% (CHF, n = 10, P < 0.05 vs C), and 93 +/- 5% (ATR APP+CHF, n = 5). The presence of CHF, or the plasma ANF levels, did not affect responses to cyclic GMP-mediated relaxing agents in PA. 4. These data indicate that the myocardial performance in CHF is not influenced by plasma ANF levels. However, altered cyclic AMP-mediated relaxation in PA during CHF is, in part, modulated by circulating ANF levels.     

Acute inflammatory response in the mouse: exacerbation by immunoneutralization of lipocortin 1.

1. An immuno-neutralization strategy was employed to investigate the role of endogenous lipocortin 1 (LC1) in acute inflammation in the mouse. 2. Mice were treated subcutaneously with phosphate-buffered solution (PBS), non-immune sheep serum (NSS) or with one of two sheep antisera raised against LC1 (LCS3), or its N-terminal peptide (LCPS1), three times over a period of seven days. Twenty four hours after the last injection several parameters of acute inflammation were measured including zymosan-induced inflammation in 6-day-old air-pouches, zymosan-activated serum (ZAS)-induced oedema in the skin, platelet-activating factor (PAF)-induced neutrophilia and interleukin-1 beta (IL-1 beta)-induced corticosterone (CCS) release. 3. At the 4 h time-point of the zymosan inflamed air-pouch model, treatment with LCS3 did not modify the number of polymorphonuclear leucocytes (PMN) recruited: 7.84 +/- 1.01 and 7.00 +/- 0.77 x 10(6) PMN per mouse for NSS- and LCS3 group, n = 7. However, several other parameters of cell activation including myeloperoxidase (MPO) and elastase activities were increased (2.2 fold, P < 0.05, and 6.5 fold, P < 0.05, respectively) in the lavage fluids of these mice. Similarly, a significant increase in the amount of immunoreactive prostaglandin E2 (PGE2; 1.81 fold, P < 0.05) and IL-1 alpha (2.75 fold, P < 0.05), but not tumour necrosis factor-alpha (TNF-alpha), was also observed in LCS3-treated mice. 4. The recruitment of PMN into the zymosan inflamed air-pouches by 24 h had declined substantially (4.13 +/- 0.61 x 10(6) PMN per mouse, n = 12) in the NSS-treated mice, whereas high values were still measured in those treated with LCS3 (9.35 +/- 1.20 x 10(6) PMN per mouse, n = 12, P < 0.05). A similar effect was also found following sub-chronic treatment of mice with LCPS1: 6.48 +/- 0.10 x 10(6) PMN per mouse, vs. 2.77 +/- 1.20 and 2.64 +/- 0.49 x 10(6) PMN per mouse for PBS- and NSS-treated groups (n = 7, P < 0.05). Most markers of inflammation were also increased in the lavage fluids of LCS3-treated mice: MPO and elastase showed a 2.47 fold and 17 fold increase, respectively (P < 0.05 in both cases); TNF-alpha showed a 11.1 fold increase (P < 0.05) whereas the IL-1 alpha levels were not significantly modified. PGE2 was still detectable in most (5 out of 7) of the mice treated with LCS3 but only in 2 out of 7 of the NSS-treated mice. 5. Intradermal injection of 50% ZAS caused a significant increase in the 2 hoedema formation in the skin of LCS3-treated mice in comparison to PBS- and NSS-treated animals: 16.7 +/- 1.5 microliters vs. 10.8 +/- 1.2 microliters and 10.2 +/- 1.0 microliters, respectively (n = 14 mice per group, P < 0.05). ZAS-induced oedema had subsided by 24 h in control animals but a residual significant amount of extravasation was still detectable in LCS3-treated mice: 4.4 +/- 0.8 microliters (P < 0.05). 6. A recently described model driven by endogenous glucocorticoids is the blood neutrophilia observed following administration of PAF. In our experimental conditions, a single bolus of PAF (100 ng, i.v.) provoked a marked neutrophilia at 2 h (2.43 and 2.01 fold) in NSS- and PBS-treated mice (n = 11), respectively, which was significantly attenuated in the animals treated with LCS3: 1.26 fold increase in circulating PMN (n = 11, P < 0.01 vs. NSS- and PBS-groups). 7. Intraperitoneal injection of IL-1 beta (5 micrograms kg-1) caused a marked increase in circulating plasma CCS by 2 h, to a similar extent in all experimental groups. In contrast, measurement of CCS levels in the plasma of mice bearing air-pouches inflamed with zymosan revealed significant differences between LCS3 and NSS-treated mice at the 4 h time-point: 198 +/- 26 ng ml-1 vs. 110 +/- 31 ng ml-1 (n = 8, P < 0.05). 8. In conclusion, we found a remarkable exacerbation of the inflammatory process with respect to both humoral and cellular components in mice passively immunised agains     

Ethnic differences in nifedipine kinetics: comparisons between Nigerians, Caucasians and South Asians.

Nifedipine was administered to 12 healthy Nigerian volunteers as a single oral dose of 20 mg capsule under fasting conditions. The pharmacokinetic results were compared with published data using the same protocol and analytical method for 27 Caucasians and 30 South Asians. The area under the plasma concentration-time curve (AUC) of nifedipine in Nigerians (808 +/- 250 ng ml-1 h) was significantly higher (P < 0.001) than that in Caucasians (323 +/- 116 ng ml-1 h) and the difference remained significant (P < 0.001) when corrected for body weight. The elimination half-life was also significantly higher (P < 0.01) in Nigerians (5.03 +/- 1.96 h) than in Caucasians (2.78 +/- 1.11 h). No significant differences were observed between Nigerians and South Asians in either AUC or half-life of nifedipine. The AUC of the nitropyridine metabolite was higher (P < 0.01) in Nigerians (220 +/- 51 ng ml-1 h) compared with that in Caucasians (154 +/- 56 ng ml-1 h) but the difference was not maintained when corrected for body weight. The AUC corrected for body weight and the elimination half-life of the metabolite were significantly higher in South Asians compared with those of Nigerians and Caucasians. The pharmacokinetics of oral nifedipine in Nigerians were similar to those in South Asians and therefore may also arise from a lower systemic clearance compared with Caucasians as has been reported previously for South Asians.     

Renal effects of TAPP, a highly selective mu-opioid agonist.

1. The effect of i.v. administration of TAPP, a highly selective and exclusively peripherally-acting mu-opioid receptor agonist, on urine output, urinary sodium, potassium and cyclic GMP, and on plasma immunoreactive atrial natriuretic factor (IR-ANF) levels was studied in conscious normally hydrated female rats (200-250 g). 2. TAPP treatment produced a significant dose-dependent increase of urine output and urinary sodium, potassium and cyclic GMP excretion during the first hour. The highest TAPP dose used (2.5 mg kg-1. body weight) elicited a 10 fold elevation of urine output from 0.23 +/- 0.06 ml h-1 to 2.5 +/- 0.3 ml h-1 (n = 18) accompanied by augmented sodium [from 17.0 +/- 4.7 mu Eq h-1 to 79 +/- 12.7 mu Eq h-1, n = 18 (P < 0.001)], potassium [from 9.5 +/- 2.5 mu Eq h-1 to 39.4 +/- 6.6 mu Eq h-1, n = 18 (P < 0.005)], and cyclic GMP excretion [from 191 +/- 21 pmol h-1 to 1340 +/- 322 pmol h-1, n = 18 (P < 0.001)]. Plasma IR-ANF rose from 22 +/- 4 pg ml-1 to 508 +/- 22 pg ml-1 (n = 18) (P < 0.001) 5 min after administration of TAPP (2500 micrograms kg-1). 3. TAPP lowered systemic blood pressure, also in a dose-related manner, 1-5 min after injection. This decrease in blood pressure was transient and did not last more than 10 min. 4. Pretreatment with the opioid antagonist naloxone (0.8 mg per rat) abolished the diuretic, natriuretic and kaliuretic effect of TAPP (250 micrograms kg-1); urine output dropped from 1.16 +/- 0.15 ml h-1, n = 12, to the control value of 0.15 +/- 0.06 ml h-1, n = 12 (P < 0.001), sodium excretion fell from 57.5 +/- 11 mu Eq h-1, to 21.3 +/- 8.5 mu Eq h-1, n = 12 (P < 0.001), and potassium excretion decreased from 45.4 +/- 9.7 mu Eq h-1, n = 12, to 16.1 +/- 7.0 mu Eq h-1, (P < 0.001). 5. Pretreatment with anti-ANF serum (0.4 ml) abolished the diuretic effect of TAPP: urine output diminished significantly from 1.93 +/- 0.28 to 0.88 +/- 0.29 ml h-1 (P < 0.01) (n = 6). The TAPP-induced diuretic action, increased sodium/potassium excretion and elevated urinary cyclic GMP levels were also reversed by anti-ANF antibodies. 6. Since TAPP is totally unable to cross the blood-brain barrier, the ensemble of these observations led to the conclusion that the diuretic, natriuretic, kaliuretic and hypotensive effects produced by this mu-opioid agonist through interaction with peripheral mu-opioid receptors occur via ANF release.     

Mechanism of 5-hydroxytryptamine-induced coronary vasodilation assessed by direct detection of nitric oxide production in guinea-pig isolated heart.

1. We assessed whether a submaximal concentration (1 microM) of 5-hydroxytryptamine (5-HT) releases nitric oxide (NO) from the coronary endothelium in guinea-pig perfused heart (n = 5 or 6/group) by direct detection of NO in coronary effluent, and determined whether this accounts for the associated coronary dilation. We also tested whether saponin is a selective and specific tool for examining the role of this mechanism in mediating agonist-induced coronary dilatation. 2. Continuous 5 min perfusion with 5-HT, or acetylcholine (ACh; 1 microM), substance P (1 nM) or sodium nitroprusside (SNP; 1 microM) increased coronary flow from baseline by 3.6 +/- 0.2, 3.4 +/- 0.2, 1.8 +/- 0.1 and 4.1 +/- 0.2 ml min-1 g-1, respectively (all P < 0.05). Coronary effluent NO content, detected by chemiluminescence, was correspondingly increased from baseline by 715 +/- 85, 920 +/- 136, 1019 +/- 58 and 2333 +/- 114 pmol min-1 g-1, respectively (all P < 0.05). 3. Continuous perfusion for 30 min with NG-nitro-L-arginine methyl ester (L-NAME) 100 microM reduced basal coronary effluent NO content by 370 +/- 32 pmol min-1 g-1 and coronary flow by 7.5 +/- 0.5 ml min-1 g-1 (both P < 0.05). Saponin (three cycles of 2 min of 30 micrograms ml-1 saponin perfusion interrupted by 2 min control perfusion) reduced basal coronary NO content by a similar amount (307 +/- 22 pmol min-1 g-1) but reduced basal coronary flow by only 0.6 +/- 0.2 ml min-1 g-1 (P < 0.05 versus the effect of L-NAME). 4. The increases in coronary flow in response to (5-HT), ACh and substance P were reduced (all P < 0.05) by 100 microM L-NAME to 1.2 +/- 0.3, 1.2 +/- 0.4 and 0.3 +/- 0.3 ml min-1 g-1, respectively. However, the flow increase in response to SNP was not reduced; it was in fact increased slightly to 4.8 +/- 0.4 ml min-1 g-1 (P < 0.05). 5. Similarly, after treatment with saponin, the increases in coronary flow in response to 5-HT, ACh and substance P were reduced to 2.1 +/- 0.3, 1.3 +/- 0.3 and 0.4 +/- 0.2 ml min-1 g-1, respectively (all P < 0.05). Again, the response to SNP was increased slightly to 4.6 +/- 0.5 ml min-1 g-1 (P < 0.05). 6. L-NAME and saponin also inhibited 5-HT, ACh and substance P-induced NO release (P < 0.05), without affecting equivalent responses to SNP. 7. For substance P, the change in coronary flow (delta CF) correlated with log10 delta NO in the presence and absence of saponin and L-NAME; delta CF = 1.2(log delta NO) 1.9; r = 0.92; P < 0.05. For 5-HT the relationship was delta CF = 2.2(log delta NO-2.7; r = 0.79; P < 0.05, indicating that 5-HT causes a disproportionately greater increase in coronary flow per release of NO. This was taken to indicate that 5-HT relaxes coronary vasculature in part by releasing NO, but in part by additional mechanisms. ACh resembled 5-HT in this respect. 8. Saponin had no effect on cardiac systolic or diastolic contractile function assessed by the construction of Starling curves with an isochoric intraventricular balloon. 9. In conclusion, despite its minimal effect on basal coronary flow, saponin is an effective tool for revealing endothelium-dependent actions of coronary vasodilator substances and has selectivity in that it does not impair endothelium-independent vasodilatation or cardiac contractile function. 5-HT dilates guinea-pig coronary arteries largely by the release of NO from the coronary endothelium.     

The pharmacokinetics of dexfenfluramine in obese and non-obese subjects.

The pharmacokinetics of dexfenfluramine (d-F) and its metabolite dexnorfenfluramine (d-NF) were compared in 10 obese (145 +/- 13 s.d. % of ideal body weight (IBW)) and 10 non-obese healthy volunteers (93 +/- 8% IBW). Each group included five men and five women, aged 28 +/- 8 years. Subjects were given single doses of d-F i.v. (15.5 mg base infused over 3 h) and orally (25.9 mg base in capsules) on separate occasions. After i.v. infusion in obese subjects, the volume of distribution (Vss) of d-F was significantly higher (969.7 +/- 393.3 l; 95% CI 688.6-1250 l) than in controls (668.7 +/- 139.6 l; 95% CI 568.9-768.5 l; P < 0.01). Clearance was not significantly different (43.9 +/- 21.0 l h-1 vs 37.3 +/- 10.6 l h-1) and the terminal half-life tended to be longer (17.8 +/- 9.4 vs 13.5 +/- 3.9 h NS). Combined data from the two groups indicated a positive correlation between Vss and % IBW (r = 0.544; P < 0.02). The oral bioavailability of d-F was 0.61 +/- 0.15 in obese subjects and 0.69 +/- 0.11 in controls. There was no significant difference between obese subjects and controls in Cmax, tmax and t1/2,z (Cmax: 20.1 +/- 6.7 and 27.3 +/- 6.2 micrograms l-1; tmax: 3.5 vs 3.0; t1/2,z: 16.5 +/- 7.1 vs 14.5 +/- 2.6 h respectively). The AUC ratio expressed in molar units for d-F/d-NF was 2.29 +/- 1.78 (i.v.) vs 1.25 +/- 0.64 (oral) in obese subjects and 2.05 +/- 1.26 (i.v.) vs 1.40 +/- 0.87 (oral) in controls.(ABSTRACT TRUNCATED AT 250 WORDS)