Indomethacin and cognitive function in healthy elderly volunteers.

1. The aim of this randomised, double-blind four way crossover study was to assess the interaction between the new calcium antagonist, lacidipine and atenolol, in patients with mild to moderate hypertension. 2. Sitting blood pressure at 4 h post-dosing with lacidipine (4 mg) and atenolol (100 mg) alone was significantly lower compared with placebo (137/89 +/- 3/3 mmHg; 142/89 +/- 5/3 mmHg; and 154/98 +/- 5/3 mmHg respectively; P < 0.001). Co-administration of both drugs produced a significant additive effect compared with atenolol and lacidipine alone (124/80 +/- 4/2 mmHg; P < 0.002). 3. Heart rate on treatment with lacidipine alone was significantly greater at 4 h compared with placebo (86 +/- 1 beats min-1 and 74 +/- 2 beats min-1 respectively; P < 0.001). When both drugs were used in combination, there was a significant decrease in pulse rate compared with lacidipine alone (58 +/- 1 beats min-1 and 86 +/- 1 beats min-1 respectively; P < 0.001). 4. Home blood pressure recordings confirmed the statistically significant reduction in blood pressure on co-dosing (120/82 +/- 10/2 mmHg) compared with lacidipine (140/92 +/- 5/3 mmHg) and atenolol (146/90 +/- 6/3 mmHg) given alone (P < 0.05). 5. Lacidipine alone produced a significant exercise tachycardia compared with atenolol alone and the atenolol/lacidipine combination (97 +/- 8 beats min-1; 65 +/- 4 beats min-1 and 75 +/- 7 beats min-1 respectively; P < 0.001). Exercise tolerance was not adversely affected by the co-administration of both lacidipine and atenolol.     

The involvement of ATP-sensitive potassium channels and adenosine in the regulation of coronary flow in the isolated perfused rat heart.

1. The roles of adenosine 5'-triphosphate (ATP)-sensitive potassium channels (KATP) and endogenous adenosine in the regulation of coronary flow have been assessed in the isolated, buffer-perfused heart of the rat. 2. In the presence of glibenclamide 10 microM there was a significant (P < 0.001) reduction in coronary flow from a baseline value of 8.78 +/- 0.76 ml min-1 g-1 to 3.89 +/- 0.59 ml min-1 g-1. This change was accompanied by a significant (P < 0.01) reduction in cardiac mechanical performance as shown by the decrease in the pressure-rate product from 21,487 +/- 2,577 mmHg min-1 to 6,950 +/- 1,104 mmHg min-1. 3. The non-selective adenosine antagonist 8-phenyltheophylline (10 microM) also caused a significant (P < 0.001) reduction in coronary flow from a basal value of 10.4 +/- 0.6 ml min-1 g-1 to 6.32 +/- 0.60 ml min-1 g-1. The subsequent addition of glibenclamide, in the presence of 8-phenyltheophylline, brought about a further significant (P < 0.001) reduction in coronary flow to 3.05 +/- 0.55 ml min-1 g-1 and this value was similar to that in the presence of glibenclamide alone. 4. In hearts perfused under constant flow conditions, exogenous adenosine caused dose-related reductions in coronary perfusion pressure described by a maximum reduction in pressure of 30.7 +/- 3.9 mmHg and an ED50 of 977 +/- 813 pmol. Addition of glibenclamide caused a significant (P < 0.01) increase in coronary perfusion pressure of 44.7 +/- 7.2 mmHg and a significant (P < 0.05) rightward shift of the dose-response curve for the depressor effects of adenosine (ED50 = 13.5 +/- 3.8 nmol), with a depression (P < 0.05) of the maximum (16.3 +/- 2.4 mmHg). 5. In conclusion, both KATP and endogenous adenosine make major contributions towards coronary vascular tone and the regulation of coronary flow in the rat isolated heart. Furthermore, in the coronary vasculature a significant proportion of the vasodilator action of adenosine is mediated through the activation of KATP.     

The cardiovascular and renal functional responses to the 5-HT1A receptor agonist flesinoxan in two rat models of hypertension.

1. This study investigated the importance of renal sympathetic nerves in regulating sodium and water excretion from the kidneys of stroke prone spontaneously hypertensive and 2K1C Goldblatt hypertensive rats anaesthetized with chloralose/urethane (17.5/300 mg initially and supplemented at regular intervals), and prepared for measurement of renal function. 2. In stroke prone spontaneously hypertensive rats, flesinoxan, 30-1000 micrograms kg-1, i.v., caused graded reductions in blood pressure and heart rate of 74 +/- 5 mmHg and 63 +/- 9 beats min-1, respectively at the highest dose (P < 0.001). Renal blood flow did not change at any dose of drug while glomerular filtration rate fell by some 20% (P < 0.001) at the highest dose of drug, absolute and fractional sodium excretions, approximately doubled at 100 micrograms kg-1, and thereafter fell to below the baseline level at 1000 micrograms kg-1. 3. This pattern of excretory response was abolished following acute renal denervation when flesinoxan caused dose-related reductions in urine flow and sodium excretion, similar to that obtained by a mechanical reduction of renal perfusion pressure. 4. Flesinoxan administration (30-1000 micrograms kg-1, i.v.) into 2K1C Goldblatt hypertensive rats caused a maximum decrease in blood pressure and heart rate (both P < 0.001) of 34 +/- 3 mmHg and 20 +/- 6 beats min-1 and while renal blood flow and glomerular filtration rate were autoregulated, from 160 to 125 mmHg, there were dose-related decreases in urine volume and sodium excretion from the clipped and non-clipped kidneys of approximately 50-60% at the highest dose. 5. These findings suggest that in the stroke prone spontaneously hypertensive rat the renal nerves importantly control sodium and water reabsorption at the level of the tubules, whereas in 2K1C Goldblatt hypertensive rats, they play a minor role.     

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.     

Effects of the calcium channel blockers, diltiazem and Ro 40-5967, on systemic haemodynamics and plasma noradrenaline levels in conscious dogs with pacing-induced heart failure.

1. Calcium channel blockers increase cardiovascular morbidity and mortality in patients with left ventricular dysfunction. These adverse effects are probably related to the negative inotropic effect of calcium channel blockers and/or a neurohormonal activation. 2. The present study was designed to examine, in conscious dogs, the acute haemodynamic and sympathetic effects of diltiazem and Ro 40-5967 (a novel calcium channel blocker) in the control state and in heart failure. 3. Thirteen dogs were instrumented with a micromanometer and an aortic catheter. After completion of experiments in the control state, heart failure was induced by right ventricular pacing (250 beats min-1, 3 weeks). Diltiazem and Ro 40-5967 were given intravenously (0.8 mg kg-1 and 1.0 mg kg-1 respectively). Cardiac output was measured by a thermodilution technique. 4. In the control state, both agents decreased similarly mean aortic pressure with significant increases in heart rate, cardiac output (both +1.0 l min-1 and P < 0.001) and plasma noradrenaline (both +55%) without changes in left ventricular dP/dtmax. In heart failure, for matched decreases in mean aortic pressure, neither diltiazem nor Ro 40-5967 changed heart rate significantly; diltiazem decreased cardiac output (-0.3 l min-1, P < 0.02) and dP/dtmax (-14%, P < 0.001) while Ro 40-5967 still increased cardiac output (+0.3 l min-1, P < 0.02) although the increased amount was smaller than in the control state. Plasma noradrenaline level was increased more during diltiazem infusion (+120%) than during Ro 40-5967 infusion (+38%, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

The cardiovascular effects of xamoterol, a beta 1-adrenoceptor partial agonist, in healthy volunteers at rest.

The cardiovascular effects of three single intravenous doses of a beta 1-adrenoceptor partial agonist, xamoterol (0.025, 0.05 and 0.1 mg kg-1) and placebo were studied in six healthy volunteers at rest using a single-blind design. In addition to heart rate and blood pressure measurements, cardiac contractility was measured by means of M-mode echocardiography and systolic time intervals. Ambulatory 24 h Holter-monitoring of the electrocardiogram was performed. Plasma concentrations of xamoterol were measured. Compared to baseline, xamoterol (0.025 mg kg-1) increased heart rate (61 +/- 3-68 +/- 3 beats min-1, means and SEM) and systolic blood pressure (119 +/- 3-138 +/- 5 mm Hg) but decreased pre-ejection period (100 +/- 4-76 +/- 5 msec). Stroke volume (88 +/- 6-104 +/- 10 ml), cardiac output (4.8 +/- 0.4-6.6 +/- 0.61 min-1), velocity of circumferential fibre shortening (1.15 +/- 0.06-1.50 +/- 0.06 circ s-1) were increased by xamoterol. No significant changes were produced by placebo. No dose-dependent effects were seen and maximum effects were produced by 0.025 mg kg-1 xamoterol. Significant effects were observed for 2 h. The areas under the plasma concentration curves (AUC0-12) showed a linear dose response. No adverse effects attributable to xamoterol were seen in haematological, biochemical, urinalysis or electrocardiographic tests. Four volunteers were aware of a more forceful heart beat after xamoterol, but this was mild and transient. It is concluded that xamoterol has a positive inotropic action.     

Preliminary investigation of the efficacy of sublingual verapamil in the management of acute atrial fibrillation and flutter.

The antiarrhythmic properties of sublingual verapamil were investigated in seven patients with acute fast atrial flutter (n = 2) or fibrillation (n = 5). A rapid and significant (P < 0.05) reduction in the ventricular rate was achieved in all seven patients. The ventricular rate at peak plasma verapamil concentration (+/- s.d.) was significantly slower than on admission (101.6 +/- 11.3 and 159 +/- 5.3 beats min-1 respectively, P < 0.01). The ventricular rate remained controlled for over 4 h. Sublingual verapamil was rapidly absorbed with the maximum peak plasma concentration (153.3 +/- 15.5 ng ml-1) being achieved after 1.21 +/- 0.18 h. Side-effects of sublingual verapamil were limited to one report of a bitter taste. The sublingual administration of verapamil may provide an alternative method for the control of acute fast atrial fibrillation and flutter in selected patients.     

Ceftazidime pharmacokinetics in preterm infants: effect of postnatal age and postnatal exposure to indomethacin.

1. The effects of postnatal age and postnatal exposure to indomethacin on the pharmacokinetic parameters of ceftazidime (CAZ) were investigated in 23 preterm infants (gestational age 28.7 +/- 1.7 weeks; weight 1086 +/- 311 g) on day 3 and day 10 after birth. 2. CAZ (25 mg kg-1) was administered by intravenous bolus injection. Blood samples were drawn from an arterial catheter at 0, 0.5, 1, 2, 4, 8, and 12 h after the dose and CAZ concentrations in serum were determined by h.p.l.c. CAZ pharmacokinetics followed a one-compartment open model. 3. The glomerular filtration rate (GFR) of all infants was studied by means of the 24 h continuous inulin infusion technique. 4. The total body clearance of CAZ (34.7 +/- 9.2 vs 50.6 +/- 19.6 ml h-1, P < 0.05; 30.7 +/- 5.9 vs 41.6 +/- 9.0 ml h-1 kg-1, P < 0.05) and GFR (0.72 +/- 0.11 vs 0.91 +/- 0.15 ml min-1, P < 0.05) increased, whereas the apparent volume of distribution (425 +/- 147 vs 352 +/- 108 ml, P < 0.05; 363 +/- 59 vs 292 +/- 44 ml kg-1, P < 0.005) and the elimination half-life (8.7 +/- 2.8 vs 5.0 +/- 0.9 h, P < 0.005) decreased significantly between day 3 and day 10 after birth. Clearance of CAZ increased with increasing GFR (r = 0.81, P < 0.001). 5. In infants with postnatal exposure to indomethacin the changes in CAZ pharmacokinetics were markedly reduced. 6. These results indicate that the dosage regimen of CAZ should be adjusted after the first week of life except in infants who were postnatally exposed to indomethacin.     

Effects of dilevalol (R,R-labetalol) compared with nifedipine on heart rate, blood pressure and muscle blood flow at rest and on exercise in hypertensive patients.

1. Dilevalol (R,R-labetalol) is a non-selective beta-adrenoceptor antagonist with beta 2-adrenoceptor agonist activity. Its effects after 1 month's administration on heart rate, blood pressure and muscle blood flow were studied in a double-blind crossover comparison with nifedipine in 16 hypertensive patients. 2. Dilevalol and nifedipine were similarly effective in lowering systolic and diastolic blood pressure at rest, but dilevalol limited the rise in systolic blood pressure induced by exercise more than nifedipine (rise of 27 vs 53 mm Hg respectively, P < 0.01). 3. Dilevalol decreased resting heart rate compared with nifedipine (73 vs 92 beats min-1 respectively, P < 0.01). Dilevalol limited the exercise induced rise in heart rate more than nifedipine (36 vs 48 beats min-1 respectively, P < 0.01). 4. Muscle blood flow (measured by strain gauge plethysmography) was not affected by either dilevalol or nifedipine at rest. After exercise, dilevalol caused an increase in excess blood flow compared with placebo (10.8 vs 5.1 ml min-1 dl-1 respectively, P < 0.01). The difference between dilevalol and nifedipine did not reach statistical significance (10.8 vs 6.5 ml min-1 dl-1 respectively, P > 0.05). 5. On blood pressure and heart rate, dilevalol demonstrated beta-adrenoceptor blocker activity at rest and on exercise. On muscle blood flow, dilevalol appeared to have no effect at rest, but may have acted as a beta-adrenoceptor blocker rather than as a beta 2-adrenoceptor agonist during exercise.     

Effect of beta-adrenoceptor blockade on atrial natriuretic peptide levels during exercise in angina pectoris.

The effects of epanolol (200 mg once daily) and diltiazem (60 mg three times daily) on the response of atrial natriuretic peptide (ANP) to exercise were investigated in a double-blind placebo-controlled crossover study in 16 patients with angina pectoris. Exercise tolerance as assessed by peak oxygen consumption was similar with all treatments. Peak heart rate (mean and 95% confidence intervals) was lower (P < 0.05) with epanolol (121 (115-130) beats min-1) than with diltiazem (137 (126-148) beats min-1) or placebo (141 (130-152) beats min-1). ANP did not change from resting values with placebo or diltiazem, but rose significantly (P < 0.05) with epanolol from 19.7 (13.0-29.8) pg ml-1 (geometric mean and 95% confidence intervals) during supine rest to 49.6 (33.7-73.0) pg ml-1 at peak exercise. Since ANP release is stimulated by atrial distension, patients with untreated angina may stop exercise before atrial dilatation occurs. With beta-adrenoceptor blockade, a reduction in peak heart rate may necessitate increased chamber volumes to maintain cardiac output, accounting for the rise in ANP.     

The renal functional responses to 5-HT1A receptor agonist, flesinoxan, in anaesthetized, normotensive rat.

1. The present study was designed to examine the effects of a centrally acting 5-HT1A receptor agonist, flesinoxan, on the cardiovascular system and renal haemodynamics and excretory function. 2. In chloralose-urethane anaesthetized Wistar rats, i.v. administration of bolus doses of flesinoxan, at 30, 100, 300 and 1000 micrograms kg-1, caused significant, dose-dependent decreases in mean arterial pressure, of 33 +/- 2 mmHg (P < 0.001) and heart rate of 57 +/- 9 beats min-1 (P < 0.001) at the highest dose used. Despite this substantial fall in perfusion pressure there were no meaningful changes in the renal excretion of water and sodium. In a second group of rats, reduction of renal perfusion pressure mechanically to the same values as observed in rats given flesinoxan (i.e. 100, 92, 84 and 76 mmHg) produced reductions in urine flow, absolute and fractional sodium excretions reaching a maximum of 74, 86 and 84% respectively (all P < 0.001) at the lowest pressure. These reductions were significantly larger than those seen in the previous group of animals. 3. In the group of rats subjected to renal denervation, flesinoxan produced changes in blood pressure and heart rate which were not different from those observed in intact animals. However, the reduction in pressure was accompanied by significant decreases in urine flow of 71%, absolute sodium excretion of 68% and fractional sodium excretion of 67% (all P < 0.001) at the highest dose, which were all significantly greater than the changes seen in the innervated animals but were not different from those observed when renal perfusion pressure was reduced mechanically.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Cardiopulmonary interactions of salbutamol and hypoxaemia in healthy young volunteers.

1. Nebulised salbutamol is frequently used in the treatment of asthma and chronic obstructive pulmonary disease. Its effects on the cardiovascular system have been extensively investigated although as yet little is known concerning its effects on the pulmonary circulation, particularly during hypoxaemia. We have therefore examined the effects of nebulised salbutamol on pulmonary haemodynamics to see if it modifies hypoxic pulmonary vasoconstriction. 2. Eight healthy normal volunteers were studied on two separate occasions. After resting to achieve baseline haemodynamics patients were randomised to receive 5 mg salbutamol or placebo via a nebuliser. They were restudied after 30 min and then rendered hypoxaemic by breathing an N2/O2 mixture to achieve an SaO2 of 75-80%. Doppler echocardiography was used to measure mean pulmonary artery pressure (MPAP), cardiac output (CO) and hence pulmonary vascular resistance (PVR). 3. Treatment with salbutamol significantly increased MPAP during normoxaemia and hypoxaemia compared with placebo at 12.0 +/- 1.2 vs 8.0 +/- 0.7 mm Hg and 28.6 +/- 0.9 vs 25.2 +/- 1.0 mm Hg, respectively (P < 0.05). Salbutamol caused a significant increase in heart rate compared with placebo and effects were additive to those of hypoxia at 74 +/- 2 vs 67 +/- 3 beats min-1 during normoxaemia and 84 +/- 3 vs 77 +/- 4 beats min-1 during hypoxaemia, respectively (P < 0.05). Whilst systemic vascular resistance fell in response to salbutamol, PVR was unchanged by salbutamol during either normoxaemia or hypoxaemia. Cardiac output was increased by salbutamol and by hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacodynamic without pharmacokinetic interaction between cicloprolol, a partial beta 1-adrenoceptor agonist, and digoxin in healthy subjects.

1. Cicloprolol is a partial beta 1-adrenoceptor agonist considered for the treatment of patients with coronary artery disease and impaired left ventricular function. In such patients, digoxin remains in widespread use. 2. We assessed the pharmacokinetic and pharmacodynamic interaction between oral cicloprolol 50 mg day-1 and oral digoxin 0.25 mg day-1 in 10 healthy male volunteers, using a double-blind, randomised protocol, during three 8 day periods. Digoxin was given alone during the first period to reach steady state; then digoxin was given with cicloprolol or placebo during the second and third periods, according to a cross-over design. 3. No significant adverse effects were observed. 4. The pharmacokinetics of digoxin were not different significantly at the end of the placebo-digoxin and cicloprolol-digoxin periods. 5. A significant increase in minimum heart rate and mean nocturnal heart rate, assessed by 24 h Holter recordings, was observed at the end of the cicloprolol-digoxin period as compared with the placebo-digoxin period (means +/- s.e. mean, 57.1 +/- 3.2 beats min-1 vs 52.2 +/- 3.1 beats min-1, P less than 0.01; and 65.6 +/- 3.8 beats min-1 vs 59.9 +/- 3.9 beats min-1, P less than 0.01, respectively). 6. A significant increase in left ventricular ejection fraction and shortening fraction, assessed by echocardiography, was noted at the end of the cicloprolol-digoxin period as compared with the placebo-digoxin period (means +/- s.e. mean, 66.4 +/- 1.4% vs 61.3 +/- 1.2%, P less than 0.05; and 37.0 +/- 1.1% vs 33.3 +/- 0.9%, P less than 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

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;...     

Plasma concentrations and effects of salbutamol administered orally to patients with cystic fibrosis.

1. To test whether cystic fibrosis (CF) altered the kinetics and dynamics of oral salbutamol, 11 patients with CF (19-33 years old; five females; FEV1: 37 +/- 12% of predicted value) and 10 healthy volunteers (20-41 years old; five females; FEV1: 99 +/- 14% of predicted value) received orally 4 mg salbutamol. 2. The estimated pharmacokinetic parameters of salbutamol in patients with CF were identical to those in healthy subjects. For instance, peak plasma concentrations of salbutamol were 10.5 +/- 2.6 (mean +/- s.d.) and 10.2 +/- 2.9 ng ml-1 (NS), and the area under salbutamol plasma concentrations as a function of time (AUC (0, 7 h)) was 43.0 +/- 9.3 ng ml-1 h and 43.3 +/- 12.7 ng ml-1 h (NS) in CF patients and in healthy subjects, respectively. Since on a mg kg-1 dose basis, CF patients received a dose 28% greater than healthy subjects, this lack of differences implies a decrease in the amount of salbutamol absorbed, or alternatively, an increase in both clearance and volume of distribution of salbutamol. 3. Salbutamol did not elicit bronchodilation in CF patients, but increased heart rate from 77 +/- 2 to 103 +/- 3 beats min-1 (P < 0.05). 4. Salbutamol decreased plasma potassium concentrations from 4.5 +/- 0.1 to 3.8 +/- 0.1 mmol l-1 in the CF group (P < 0.05) and from 4.1 +/- 0.2 to 3.4 +/- 0.1 mmol l-1 in the controls (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of a converting enzyme inhibitor (captopril) and angiotensin II on fetal renal function.

1. Renal function was studied in chronically catheterized fetal sheep (119-128 days gestation), before and during treatment of the ewe with the angiotensin converting enzyme (ACE) inhibitor, captopril, which crosses the placenta and blocks the fetal renin angiotensin system. 2. An i.v. dose of 15 mg (about 319 micrograms kg-1) of captopril to salt-replete ewes followed by an infusion to the ewe of 6 mg h-1 (about 128 micrograms kg-1 h-1) caused a fall in fetal arterial pressure (P < 0.01), and a rise in fetal renal blood flow (RBF) from 67.9 +/- 5.6 to 84.9 +/- 8.3 ml min-1 (mean +/- s.e. mean) (P < 0.05). Renal vascular resistance and glomerular filtration rate (GFR) fell (P < 0.01); fetal urine flow (P < 0.01); fetal urine flow (P < 0.01) and sodium excretion declined (P < 0.05). 3. Ewes were treated for the next 2 days with 15 mg captopril twice daily. On the 4th day, 15 mg was given to the ewe and fetal renal function studied for 2 h during the infusion of captopril (6 mg h-1) to the ewe. Of the 9 surviving fetuses, 3 were anuric and 3 had low urine flow rates. When 6 micrograms kg-1 h-1 of angiotensin II was infused directly into the fetus RBF fell from 69 +/- 10.1 ml min-1 to 31 +/- 13.9 ml min-1, GFR rose (P < 0.05) and urine flow (P < 0.01) and sodium excretion increased in all fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)     

The dose dependency of the alpha- and beta-adrenoceptor antagonist activity of carvedilol in man.

1. The alpha- and beta-adrenoceptor antagonist activity of carvedilol, a beta-adrenoceptor antagonist with vasodilating properties, and labetalol were investigated in 10 healthy male subjects. They received infusions with serially increasing concentrations of isoprenaline and phenylephrine before and after single oral doses of carvedilol 6.25, 12.5 and 25 mg, labetalol 400 mg and placebo at weekly intervals in a double-blind randomised manner. An exercise step test was performed at the end of the infusions. 2. The dose of isoprenaline required to increase heart rate by 25 beats min-1 (I25) and the dose of phenylephrine required to increase systolic and diastolic blood pressure by 20 mm Hg (PS20 and PD20) were calculated using a quadratic fit to individual dose-response curves. Comparisons were made with placebo and P < 0.05 was considered significant. 3. The I25 was increased by carvedilol 25 mg and labetalol 400 mg (P < 0.05). The dose ratios at I25 were: carvedilol 6.25 mg 2.1 +/- 1.6, carvedilol 12.5 mg 3.1 +/- 1.9, carvedilol 25 mg 6.4 +/- 4.9 and labetalol 400 mg 8.8 +/- 4.4. 4. The PS20 was increased by labetalol 400 mg (P < 0.05). The dose ratios at PS20 were: carvedilol 6.25 mg 1.0 +/- 0.2; 12.5 mg, 1.2 +/- 0.2; 25 mg, 1.3 +/- 0.4 and labetalol 400 mg 2.2 +/- 0.8. 5. The PD20 was increased by labetalol 400 mg (P < 0.05). The dose ratios at PD20 were: carvedilol 6.25 mg 1.1 +/- 0.3; 12.5 mg, 1.3 +/- 0.3; carvedilol 25 mg 1.3 +/- 0.4 and labetalol 400 mg 2.1 +/- 0.8.(ABSTRACT TRUNCATED AT 250 WORDS)     

Location of the mechanism of the clonidine withdrawal tachycardia in rats

Withdrawal of chronic infusion of clonidine elicits severe tachycardia and short-lasting blood pressure elevations (upswings). Withdrawal of clonidine in low dosage (30 micrograms kg-1 day-1 i.c.v., 7 days) elicited a maximum of 10.9 +/- 0.5 upswings h-1. Cessation of s.c. infusion of clonidine (30 micrograms kg-1 day-1 7 days) evoked a maximum of 1.9 +/- 0.5 upswings h-1. After cessation of the two clonidine infusions no overshoot of heart rate occurred. Withdrawal of a higher dose of clonidine (300 micrograms kg-1 day-1 s.c., 7 days), however, induced tachycardia (from 302 +/- 8 to 433 +/- 8 beats min-1) and 7.6 +/- 1.4 upswings h-1. The administration of the alpha 2-adrenoceptor antagonist yohimbine precipitated withdrawal tachycardia in animals treated with oxymetazoline, a hydrophilic alpha-adrenoceptor agonist. Yohimbine (3 mg kg-1 i.p.) precipitated a severe rise in heart rate from 285 +/- 14 to 520 +/- 5 beats min-1 in oxymetazoline (300 micrograms kg-1 day-1 s.c., 7 days) treated rats and from 320 +/- 13 to 420 +/- 11 beats min-1 in saline-treated animals. Upswings were not induced by yohimbine treatment. It is concluded, that the blood pressure upswings after clonidine withdrawal are due to a central mechanism, whereas the mechanism of the overshoot of heart rate is located peripherally, probably at the cardiac presynaptic level.     

Stereoselective disposition of (+/-)-sotalol at steady-state conditions.

The objective of this study was to assess, under steady-state conditions, the stereoselective disposition of (+/-)-sotalol in man. In all patients studied (n = 7) values of oral clearance (137 +/- 51 ml min-1), renal clearance (96 +/- 42 ml min-1) and nonrenal clearance (41 +/- 25 ml min-1) of (-)-sotalol were greater than those for (+)-sotalol (123 +/- 45 ml min-1, 89 +/- 39 ml min-1 and 34 +/- 23 ml min-1, respectively; P < 0.05, Student's paired t-test). Binding to plasma proteins was greater for (+)-sotalol (38 +/- 9% vs 35 +/- 9% for the (-)-enantiomer; P < 0.05) such that unbound oral clearance (+)/(-) ratio (0.95 +/- 0.06) and unbound renal clearance (+)/(-) ratio (0.97 +/- 0.06) were not stereoselective. In contrast, estimated unbound nonrenal clearance, which represents approximately 25% of the total unbound clearance of the drug, was greater for the (-)-enantiomer (64 +/- 42 ml min-1) compared with (+)-sotalol (57 +/- 42 ml min-1; P < 0.05). The difference in the pharmacokinetics of sotalol enantiomers is mainly related to stereoselectivity in plasma protein binding.