Drugs and the liver. I. Effects of glutethimide and phenobarbital on hepatic bilirubin clearance, plasma bilirubin turnover and carbon monoxide production in man

The effects of glutethimide and phenobarbital on the plasma unconjugated bilirubin concentration, hepatic bilirubin clearance (C_BR) and plasma bilirubin turnover (BRT) were determined in 19 patients with mild chronic unconjugated hyperbilirubinemia (Gilbert's syndrome) and 11 normal volunteers. C_BR and BRT were calculated from plasma radio-bilirubin disappearance curves obtained both before and during drug administration. The response to both drugs was essentially identical. During drug administration, the patients with Gilbert's syndrome attained a new steady state in which the plasma unconjugated bilirubin concentration $\text{(}\text{BR}\text{)}\text{was}\text{30 ± 2\% (}\text{mean}\text{±}\text{S.E.M.}$) and C_BR 314 ± 25% of baseline. In the normal volunteers, $\text{BR}$ fell to 65 ± 6%, while C_BR increased to 135 ± 9% of baseline during the period of drug administration. Although neither total red cell volume nor the half-life of ⁵¹Cr-labeled erythrocytes was altered by either agent, daily plasma bilirubin turnover fell significantly (P < 0.05) to 87 ± 4% of baseline in the 30 subjects studied, and endogenous carbon monoxide production, which provides an independent estimate of the rate of heme degradation and bilirubin formation, was 93 ± 5 % of control (0.2 > P > 0.1). These studies indicate that both accelerated hepatic bilirubin clearance and reduced plasma bilirubin turnover contribute to the reduction in bilirubin concentration observed during administration of phenobarbital and glutethimide. The methods employed provided no evidence that these agents produce an increase in the rates of heme catabolism, bilirubin production or carbon monoxide formation.     

Dimethyl sulfoxide: Inhibition of acetylcholinesterase in the mammalian heart

The heart rate of the isolated, perfused, working rat heart was significantly and equally depressed by 1 × 10^?6 M acetylcholine (ACh) and by 6 × 10^?5 M 4-ketoamyltrimethylammonium (4K), a cholinomimetic agonist. Dimethyl sulfoxide (DMSO) (10 μl/ml, 140 mM) strongly potentiated the effect of ACh but did not alter the effect of 4K. DMSO (10 μl/ml, 140 mM final concentration) alone had no significant effect upon heart rate when added to the perfusate in incremental additions of 1 μl · (ml perfusate)^?1 · min^?1 over a 10-min period. The specific activity of atrial homogenate cholinesterase was $\text{48.8 ± 3.46}\text{nmoles}\text{·}\text{min}{}^{\mathrm{?1}}\text{· (}\text{mg protein}\text{)}{}^{\mathrm{?1}}\text{(}\text{mean}\text{±}\text{S.E.M.}\text{), 38.2 ± 1.60}$ for butyrylcholinesterase, and 11.2 ± 0.86 for acetylcholinesterase (AChE). True AChE activity (measured in the presence of a maximally effective concentration of tetraisopropylpyrophosphoramide) had a V_max of 13.4 ± 0.17 nmoles · min^?1 · (mg protein)^?1 and an apparent K_m value of 1 × 10^?4 M acetylthiocholine. At this K_m substrate concentration, DMSO inhibited atrial AChE activity (I₅₀ = 9 μl/ml). At the concentration tested, DMSO inhibited atrial AChE and potentiated ACh effects.     

Metabolic rate of phenacetin and of paracetamol in dogs before and after treatment with phenobarbital or skf 525 A

In six male mongrel dogs the apparent biological half life ($\text{t}\text{2}$) in plasma of intravenously injected phenacetin decreased from 34·6 to 27·2 min after treatment with phenobarbital (25 mg/kg/day for 8 days) (P < 0·025). In the same dogs, the apparent $\text{t}\text{2}$ of intravenously injected phenazone decreased from 78·6 to 32·4 min (P < 0·05). Treatment with SKF 525 A (25 mg/kg) increased the $\text{t}\text{2}$ of phenazone in three other dogs from 70·6 to 246·7 min, whereas the $\text{t}\text{2}$ of phenacetin remained unaffected.The concentration of phenacetin at zero time of intravenous injection increased from 29·5 ± 5·9 S.E. to 43·5 ± 12·6 μg/ml plasma (P < 0·2) after phenobarbital treatment; pretreatment with phenobarbital, however, had no influence on the mean concentration of phenazone at 0 time. SKF 525 A did not influence the zero time concentration of either phenacetin or phenazone.Beagle liver microsomal protein and cytochrome P-450 concentrations increased from 3·2 to 4·2 mg/ml and from 1·0 to 4·1 n-mole/mg protein, respectively, after phenobarbital treatment. Treatment with phenobarbital had no influence on the rates of formation of paracetamol and p-phenetidin nor was the apparent K_m of phenacetin affected.The binding of phenacetin to blood constituents increased from 50 per cent at 5 μg/ml to 59 per cent at 1 μg phenacetin/ml. In the presence of 30 μg phenobarbital/ml blood, the binding of phenacetin at 1 μg/ml blood decreased by 22 per cent.It is concluded that the decrease of the apparent $\text{t}\text{2}$ of phenacetin in dog plasma after phenobarbital treatment may be due to a change in the apparent volume of distribution and/or to some stimulation of an NADPH-dependent enzyme system of the liver less affected by treatment with SKF 525 A than in other species.     

Early postoperative gastric enteral nutrition improve gastric emptying after cardiac surgery

Postoperative intragastric enteral feeding in cardiac surgery patients is frequently complicated by delayed gastric emptying. The aim of the study was to evaluate how early postoperative gastric enteral nutrition affects the gastric emptying in coronary artery by-pass graft (CABG) surgery patients. In the prospective, randomized study 40 patients treated at intensive care unit after CABG surgery were studied. Patients were divided in two groups: enteral feeding group E (20 patients: age 59±8 yr.; male 70%) and control group C (20 patients: age 58±10 yr.; male 80%), respectively. Paracetamol absorption test was used to evaluate gastric emptying. In the group E postoperative gastric supply of enteral formula begun 18 hours after surgery and after 6 hours the supply was stopped and paracetamol solution was administrated by nasogastric tube. The patients in group C for.rst 24 hours received only crystalloid solutions intravenously and paracetamol solution by nasogastric tube. Blood samples were obtained at 0 (t₀), 15 (t₊₁₅), 30 (t₊₃₀), 60 (t₊₆₀) and 120 (t₊₁₂₀) min after administration of paracetamol. The values of plasma paracetamol concentration (PPC) at 15 and 120 min were significantly higher in group E vs. group C: (t₊₁₅) 3.3_±2.5 vs. 1.7±1.9 and (t₊₁₂₀) 5.2_−2.8 vs. 3.3_±1.6 (p <0.05). The PPC values at 30 and 60 min were higher, but not signi.cantly, in group E vs. group C: (t₊₃₀) 3.7±2.0 vs. 2.9±2.7 and (t₊₆₀) 5.1±3.2 vs. 3.9±3.5 (p = NS). The area under the PPC curve was 429 ± 309 in the E group vs. 293 ± 204 in the group C (p < 0.05). In conclusion an early postoperative gastric administration of nutritients after CABG surgery stimulates the gastric emptying.     

Pharmacokinetics and penetration of moxifloxacin into infected diabetic foot tissue in a large diabetic patient cohort

Objectives

Physiological changes occurring in patients with diabetes may affect the pharmacokinetics and penetration of antimicrobial agents into peripheral tissue. We examined the pharmacokinetics and the penetration of moxifloxacin into perinecrotic tissue of diabetic foot lesions in patients with diabetic foot infections (DFI).

Patients and methods

Adult patients suffering from type 2 diabetes mellitus and hospitalized for DFI (Texas classification of at least B2) were treated with 400?mg moxifloxacin intravenously (IV) or orally (PO) once daily. The pharmacokinetics of moxifloxacin and its concentration 3 h after administration in samples of perinecrotic tissue resected from infected diabetic foot wounds were determined at steady state (days 4?C8).

Results

A total of 53 patients with diabetes mellitus type 2 (mean age 69.4?±?10.8?years) were included in the study, of whom 28 received PO and 25 IV moxifloxacin therapy for a median of 8?days. In the PO and IV subgroups, the mean maximum observed plasma concentration (C _max) in plasma was 2.69 and 4.77?mg/l at a median of 2 [time to reach C _max (T _max) range 1.0?C8.0?h] and 1?h after administration, respectively. A mean area under the plasma concentration?Ctime curve from time 0 until the last quantifiable plasma concentration (AUC_0-24?h) of 29.36?mg h/l (PO) and 27.09?mg h/l (IV) was achieved. Mean moxifloxacin concentrations in perinecrotic tissue of infected diabetic foot wounds following PO or IV administration were 1.79?±?0.82?and 2.20?±?1.54???g/g, thus exceeding the MIC₉₀ (minimum inhibitory concentration required to inhibit growth of 90% of organisms) for Staphylococcus aureus (0.25?mg/l) by seven- and eightfold and the MIC₉₀ for Escherichia coli (0.06?mg/l) by 29-fold and 36-fold, respectively. The mean tissue-to-plasma ratios of moxifloxacin concentration 3?h after administration were 1.01?±?0.57 (PO) and 1.09?±?0.69 (IV). Significant differences between the routes of administration were observed for T _max and C _max (P?<?0.01), but not for other clinically relevant parameters (AUC_0-24; moxifloxacin DFI tissue concentration).

Conclusions

The plasma concentration?Ctime curve of moxifloxacin in diabetic patients is similar to that of healthy volunteers. We also observed a good penetration of moxifloxacin into inflamed DFI tissue which taken together with the possibility of sequential IV/PO therapy suggest that moxifloxacin 400?mg once daily is a therapeutic option in the treatment of DFI caused by susceptible organisms.     

高效液相色谱法测定大鼠血浆和子宫中黄体酮及其代谢物的浓度

目的建立高效液相色谱法测定大鼠血浆和子宫样品中的黄体酮及其代谢物20α-羟基黄体酮,并研究大鼠肌肉注射黄体酮后血浆和子宫中的药物代谢动力学。方法样品经液-液萃取后,以乙腈-水(60∶40,pH 4.0)为流动相,用ODS柱进行分离,240 nm检测。以18-甲基炔诺酮为内标。结果血浆中黄体酮C_max为(508±62) μg·L^-1,T_max为(3.2±0.4) h,T_1/2(k_e)为(10±4) h,AUC_0-48h为(5 886±1 573) μg·L^-1·h,子宫中黄体酮T_max为(5.2±1.1) h,C_max(1.7±1.1) μg·g^-1。20α-羟基黄体酮具有与黄体酮相似的T_max。结论该方法简便、准确,可同时测定黄体酮和代谢物,适用于黄体酮及其代谢物20α-羟基黄体酮的药代动力学研究。     

Pharmacokinetics and tissue disposition of danofloxacin in sheep

The plasma pharmacokinetics of danofloxacin administered at 1.25 mg kg⁻¹ body weight by the intravenous and intramuscular routes were determined in sheep. Tissue distribution was also determined following administration by the intramuscular route at 1.25 mg kg⁻¹ body weight. Danofloxacin had a large volume of distribution at steady state (V_ss) of 2.76±0.16 h (mean±S.E.M.) L kg⁻¹, an elimination half-life (t_1/2β) of 3.35±0.23 h, and a body clearance (C1) of 0.63±0.04 L kg⁻¹ h⁻¹. Following intramuscular administration it achieved a maximum concentration (C_max) of 0.32±0.02 μg mL⁻¹ at 1.23±0.34 h (t_max) and had a mean residence time (MRT) of 5.45±0.19 h. Danofloxacin had an absolute bioavailability (F) of 95.71±4.41% and a mean absorption time (MAT) of 0.81±0.20 h following intramuscular administration. Mean plasma concentrations of >0.06 μg mL⁻¹ were maintained for more than 8 h following intravenous and intramuscular administration. Following intramuscular administration highest concentrations were measured in plasma (0.43±0.04 μg mL⁻¹), lung (1.51±0.18 μg g⁻¹), and interdigital skin (0.64±0.18 μg g⁻¹) at 1 h, duodenal contents (0.81±0.40 μg mL⁻¹), lymph nodes (4.61±0.35 μg g⁻¹), and brain (0.06±0.00 μg mL⁻¹) at 2 h, jejunal (10.50±4.31 μg mL⁻¹) and ileal (5.25±1.67 μg mL⁻¹) contents at 4 h, and colonic contents (8.94±0.65 μg mL⁻¹) at 8 h. © 1998 John Wiley & Sons, Ltd.     

High inter-individual variability of vardenafil pharmacokinetics in patients with pulmonary hypertension

Purpose

To evaluate the pharmacokinetic parameters of a single oral dose of vardenafil in patients with pulmonary hypertension (PH).

Methods

Sixteen patients with PH received vardenafil in single oral doses (20, 10 or 5 mg), and repeated blood sampling for up to 9 h was performed. Vardenafil plasma concentration was determined using liquid chromatography tandem mass spectrometry. Pharmacokinetic parameters were calculated using model-independent analysis.

Results

The plasma vardenafil concentration increased rapidly and exhibited a median time to maximum plasma concentration (t_max) of 1 h and a mean elimination half-life (t_1/2) of 3.4 h. The geometric mean and standard deviation of (1) the peak plasma concentration (C_max) was 21.4?±?1.7 μg/L, (2) the normalized C_max (C_{max, norm}) 79.1?±?1.6 g/L, (3) the area under the time–concentration curve (AUC) 71.5?±?1.6 μg · h/L and (4) the normalized AUC (AUC_norm) 261.6?±?1.7 g · h/L. Patients co-medicated with bosentan reached t_max later and had a 90% reduction of C_max, C_{max, norm}, AUC and AUC_norm.

Conclusion

The pharmacokinetic profile of vardenafil overall revealed considerable inter-individual variability in patients with PH. Co-medication with bosentan resulted in a pharmacokinetic drug interaction, leading to significantly decreased plasma concentrations of vardenafil. Therapeutic drug monitoring for individual dose optimization may be warranted.     

Effects of chlorpromazine and atropine on acetaminophen absorption in rabbits

The effects of chlorpromazine and atropine on the gastrointestinal absorption of acetaminophen were investigated in rabbits. Two doses of chlorpromazine and atropine were injected intraperitoneally 30 min prior to the oral administration of acetaminophen. Blood samples were collected before and 0.25,0.5,0.75, 1.0,1.5,2,3,4,5 and 6 h after acetaminophen administration and were analyzed for acetaminophen contents using a HPLC method. Chlorpromazine at a 10 mg/kg dose significantly reduced the maximum plasma concentration (C_max) of acetaminophen from 64.2 ± 2.8 to 40.0 ± 6.3 μgg/ml(P < 0.05). In addition, chlorpromazine at 5 and 10 mg/kg doses significantly increased the time taken to reach the maximum plasma concentration (T_max) of acetaminophen from 0.29 ± 0.04 to 0.67 ± 0.15 and 0.96 ± 0.21h, respectively (P < 0.05). Atropine at 0.5 and 1.0 mg/kg doses also significantly reduced the C_max of acetaminophen from 69.6 ± 4.7 to 45.6 ± 3.7 and 45.9 ± 6.7 μg/ml, respectively (P < 0.05). However, atropine has little effect on T_max of acetaminophen. Both chlorpromazine and atropine did not seem to affect the area under the plasma concentration-time curve and the elimination half-life of acetaminophen. It was concluded that chlorpromazine and atropine affect the rate but not the extent of acetaminophen absorption, by delaying the gastric emptying.     

Sustained-release interleukin-2 following intramuscular injection in rats

A potential sustained-release recombinant interleukin-2 (rIL-2) formulation was evaluated following intramuscular (i.m.) injection in rats. Poloxamer 407 (Pluronic® F-127) is a block copolymer comprised of polyoxyethylene and polyoxypropylene segments which exhibits the property of reverse thermal gelation. Thus, an rIL-2/poloxamer 407 preparation was injected i.m. in rats as a viscous mobile solution with subsequent gelation in vivo. Resultant plasma rIL-2 concentration-time data indicated absorption rate-limited disposition of rIL-2 following i.m. injection. The mean values of the absorption rate constant (k_clim were 0.64 ± 0.073 and 0.21 ± 0.019 h⁻¹ following i.m. injection of an rIL-2 aqueous solution and the HL-2 gel formulation, respectively. The mean values of the elimination rate constant (k_elim) were 1.76 ± 0.22 and 1.21 ±0.079 h⁻¹ following administration of rIL-2 as an aqueous solution or gel formulation, respectively. The blood sampling time point at which the greatest plasma rIL-2 concentration (C_max.) was observed was 2 h for rats injected i.m. with rIL-2 formulated in poloxamer 407 compared to 1 h for rats injected i.m. with an rIL-2 aqueous solution. The mean value of the C_max. was significantly (p < 0.05) less in rats injected i.m. with the rIL-2 gel formulation (C_max= 12500 ± 1450 pg/ml) compared to rats injected i.m. with an aqueous solution of rIL-2 (C_max = 19 600 ± 2650 pg/ml). The bioavailability of rIL-2 when injected i.m. as an rIL-2/poloxamer gel formulation relative to an i.m. injection of an rIL-2 aqueous solution was approx. 1.0. Cumulative amounts of rIL-2 recovered in the urine 48 h after an i.m. injection of either an rIL-2 aqueous solution or rIL-2 gel formulation were less than 1 percent of the administered dose. Since the rIL-2/poloxamer formulation evaluated in this study resulted in a decrease in the maximum blood concentration of rIL-2 achieved and an increase in the time required to reach a maximum blood concentration, without a reduction in the bioavailability of the protein, the rIL-2 gel formulation may represent an alternative, sustained-release mode of rIL-2 administration.     

Biopharmaceutics: Drug Metabolism and Pharmacokinetics: Circadian Variations in the Pharmacokinetics of Pentoxifylline in Man

Optimization of therapy by chronopharmacology requires knowledge of rhythmic manifestations of disease activity and chronopharmacokinetic data of the drugs prescribed. Rhythmic functioning of the cardiovascular system in healthy and diseased subjects is manifested as circadian rhythms in blood pressure, cardiac output, heart rate, etc. The disposition of several cardiovascular drugs in man has been reported to be time-dependent. This study reports the effect of time of administration on the disposition of pentoxifylline. Twelve healthy volunteers were treated with 400 mg pentoxifylline orally at 0100, 0700, 1300 and 1900 h in a randomized crossover Latin-square design with a wash-out period of one week. Serum samples were analysed for unchanged pentoxifylline by HPLC. Pharmacokinetic parameters were calculated using a model-independent method. The mean values of various pharmacokinetic parameters after drug treatment at these times were, respectively: maximum plasma concentration (C_max) 485 ± 174, 646 ± 175, 735 ± 271 and 781±217 ng mL^?1; time to reach the maximum plasma concentration (T_max) 1.90±0.39, 1.66±0.4, 1.31 ± 0.41 and 1.32 ± 0.44 h, mean residence time (MRT) 3.8 ± 0.8, 2.9 ± 0.5, 2.9 ± 0.4 and 2.7 ± 0.3 h, elimination half-life (t1/2) 1.93 ± 0.86, 1.23 ± 0.3, 1.39 ± 0.3 and 1.23 ± 0.18 h and volume of distribution at steady state (Vd_ss/f) 11991 ± 4862, 8823 ± 3484, 8275 ± 2357 and 7063 ± 1950 mL kg^?1. The mean C_max value was significantly (P < 0.05) lower after drug administration at 0100 h than after other time-points whereas mean T_max, MRT, Vd_ss/f and t1/2 values were significantly (P < 0.05) higher. These variations might be because of time-dependent changes in absorption and biliary excretion of pentoxifylline and should be borne in mind when designing sustained action dosage forms for the drug.     

Repeated dose pharmacokinetics of pancopride in human volunteers

The aim of this study was to assess the pharmacokinetic profile of pancopride after repeated oral dose administration of 20 mg pancopride in tablet form once a day for 5 d in 12 healthy male volunteers. Plasma levels were measured by HPLC using a solid phase extraction method and automated injection. The minimum quantification limit of pancopride in plasma was 2 ng mL^?1. The maximum plasma concentration (mean ± SD) after the first dose was 92.5 ± 41.5 ng mL^?1 and t_max was 1.7 ± 0.9 h. The elimination half-life (t_1/2) was 14.3 ± 6.9 h. The area under the concentration-time curve from zero to infinity (AUC) was 997 ± 396 ng h mL^?1. The maximum plasma concentration (mean ± SD) at steady state (day 5) was 101.8 ± 36.9 ng mL^?1 and t_max was 2.2 ± 1.2 h. The elimination half-life (t_1/2) was 16.3 ± 2.7 h and the minimum plasma concentration (C) was 16.6 ± 6.9 ng mL^?1. The area under the concentration-time curve during the dosing interval (AUC) was 995 ± 389 ng h mL^?1. The average plasma concentration at steady state (C) was 43.3 ± 16.1 ng mL^?1 and the experimental accumulation ratio (R_AUC) was 1.34 ± 0.19, whereas the mean theoretical value (R) was 1.40 ± 0.29. The results obtained showed a good correlation between the experimental plasma levels and the expected values calculated using a repeated dose two-compartment model assessed by means of the Akaike value. It is concluded that the pharmacokinetics of pancopride are not modified after repeated dose administration. The safety parameters showed no clinically relevant alterations.     

In-vivo Distribution and Erythrocyte Binding Characteristics of Cyclosporin in Renal Transplant Patients

The pharmacokinetic parameters of cyclosporin, a potent immunosuppressive agent, show large intra-and inter-individual variability, possibly because of the different analytical methods used. A recently developed cyclosporin-specific radioimmunoassay has been used to study the in-vivo distribution and binding characteristics of cyclosporin in whole blood, plasma and erythrocytes of fifteen renal transplant patients. The profiles of cyclosporin concentration-time curves after an oral dose of cyclosporin had either one peak (ten patients, group A) or two (five patients, group B). Essentially no difference was observed between the two groups in the relationship between equilibrium cyclosporin concentrations in erythrocyte and plasma as a function of whole-blood concentration. The equilibrium in-vivo cyclosporin concentrations in erythrocytes and plasma were, however, markedly lower than those previously observed under in-vitro conditions. The ratio of cyclosporin concentration in erythrocytes (C_E) to that in plasma (C_P) changed with time, in inverse proportion to the change in cyclosporin concentration in blood, over the range 0.63-2.80 in individual patients with an average of 1.36 ± 007 (mean ± s.e.m.) for group A and 1.42 ± 0.23 for group B. The apparent cyclosporin binding affinity (K_d) to erythrocytes under in-vivo conditions averaged 452.2 ± 47.6 nm (543.5 ± 57.2 ng mL^?1) for group A and 419.4 ± 41.2 nm (504.1 ± 49.5 ng mL^?1) for group B, whereas apparent cyclosporin binding capacity (B_max) of the blood cell averaged 0.83 ± 0.07 nmol mL^?1 for group A and 0.78 ± 0.07 nmol mL^?1 for group B. Significantly reduced average K_d (262.7 ± 40.2 nm or 315.8 ± 48.9 ng mL^?1, P < 001) and B_max (0.56 ± 008 nmol mL^?1, P < 005) values were observed during the period after T_max (4–12 h after the drug ingestion) in group A patients. Apparent K_d and B_max, determined by a nonlinear regression technique, were 131.6 ± 29.4 and 1088.0 ± 114.7 nm (158.2 ± 35.4 and 1307.8 ± 137.9 ng mL^?1) and 0.178 ± 0.024 and 0.814 ± 0.078 nmol mL^?1, respectively, during the 4–12 h period in group A patients. These findings reveal distinct differences in in-vivo distribution of cyclosporin and the binding characteristics of the compound to erythrocytes from those previously observed under in-vitro conditions. The significantly lower K_d of cyclosporin binding to erythrocytes during the elimination phase suggests a potential effect of cyclosporin-containing erythrocytes or of cyclosporin contained in erythrocytes during cyclosporin treatment.     

beta-adrenergic receptors of human leukocytes: studies with intact mononuclear and polymorphonuclear cells and membranes comparing two radioligands in the presence and absence of chloroquine

Owing to the large differences in reported values for β-adrenergic receptor numbers and binding affinity in normal leukocytes, we undertook a systematic re-examination of the binding of two widely used beta antagonists, (-)-[³H]dihydroalprenolol (DHA) and $\text{(±)-}\text{[}{}^{125}\text{I]iodohydroxybenzylpindolol}$ (HYP), to intact normal mononuclear (MN) leukocytes and polymorphonuclear (PMN) leukocytes and membrane preparations. Assays were conducted in the presence and absence of chloroquine, which has been proposed recently to eliminate ligand uptake into a non-receptor cell compartment such as lysosomes. The binding curves relating radioligand concentration to specific sitesper intact cell were biphasic. At high (10–24 nM) (-)-DHA ligand concentration in the absence of chloroquine, a large number (20,000–60,000 sites/cell) of low affinity (K_d 12–15 nM) stereospecific binding sites were detected in both cell types. This class of binding sites was eliminated by 10 ,μM chloroquine not only in PMN cells but also in the lysome-poor MN cells (? 90% lymphocytes), leaving 2000–3000 specific high affinity (-)-DHA sites/cell. In the absence of chloroquine, comparably low numbers of specific high affinity binding sites/cell were also obtained by the use of appropriately low concentrations of (-)-DHA or (±)-HYP (800 pM or less). However, even at these low radioligand concentrations chosen to measure high affinity specific binding, the addition of 10 μM chloroquine produced a moderate reduction in the number of sites/cell, without a detectable change in the apparent K_d. Mean (± S.E.M.) site numbers obtained in the presence of chloroquine were: 1331 ± 100 sites/MN cell and 1135 ±129 sites/PMN cell (K_d 143–153 pM) using (-)-DHA; and 1487 ± 210 sites/MN cell and 1065 ± 69 sites/PMN cell [avg. K_d(±) 224–274 pM] using (±)-HYP. Chloroquine had no effect on agonist-stimulated cAMP production but produced an apparent increase in the effectiveness of (-)-propranolol as an inhibitor of DHA binding. Competition studies on the binding of DHA and HYP with zinterol and practolol confirmed that the receptor was of the β₂-subtype for both MN and PMN cells. The detection of a moderately larger number of high affinity binding sites at saturation (Scatchard analysis) by (±)-HYP than by (-)-DHA was a consistent finding with either intact cells or membranes, with or without chloroquine. The possible overestimation of receptor numbers by a racemic ligand such as (±)-HYP is discussed and leads us to favor the use of a pure stereoisomer such as (-)-DHA. A system employing 800 pM (-)-[³H]DHA, 1 ,μM (-)-propranolol and 10, μM chloroquine with intact MN and PMN cells yielded reproducible and plausible results. Our values for β-adrenergic receptor numbers of intact MN and PMN cells and membranes are compared to others in the literature.     

Concentration of DDT and DDE in plasma and subcutaneous adipose tissue before and after intestinal bypass operation for treatment of obesity

DDT and its principal metabolite, DDE, are stored mainly in body fat. In spite of a general prohibition in household use in 1970, the general population in Sweden is still exposed to these pesticides in the diet. The aim of this study was to examine whether weight loss is followed by increased concentrations of the pesticides in adipose tissue and plasma and whether increased concentrations could possibly explain some unusual neurological symptoms observed in some patients after a shunt operation. Eight subjects were examined before and 1 year after jejuno-ileostomy. The mean weight loss was 46.9 ± 2.8 kg ($\text{X}\text{+}\text{SE}$). The concentrations of p,p′-DDE in plasma increased significantly from 5.1 ± 0.9 to 8.2 ± 1.3 ng/ml during the weight loss. This concentration is still well below the concentration in a control group of nonexposed office personnel whose mean concentration is 19 ± 4.0 ng/ml. In adipose tissue the mean concentrations of p,p′-DDT and p,p′-DDE increased from 390 ± 65 to 526 ± 107 ng/g and 863 ± 136 to 1341 ± 194 ng/g, respectively. The ratio of DDE: DDT increased in all but one subject, indicating an increased metabolism of DDT after the operation.The calculated total body content of DDT and DDE decreased in all but two patients after the bypass operation due to increased metabolism and excretion.The risk of DDT intoxication following an intestinal bypass operation appears to be small.     

Modification by beet and cabbage diets of aflatoxin B1-induced rat plasma α-foetoprotein elevation,hepatic tumorigenesis,and mutagenicity of urine

Weanling male Fischer rats were fed a purified diet or diets containing 25% (w/w) freeze-dried ground beets or cabbage with or without 1 ppm aflatoxin B₁ (AFB₁) for 26 wk. In 3–7 wk the cabbage diet diminished, while the beet diet enhanced AFB₁-induced plasma α-foetoprotein (AFP) elevation. When the experiment was extended to 42 wk by maintaining the animals on the purified (basal) diet for a further 16 wk the rats that had consumed AFB₁ in the beet diet had 72 ± 14 tumours/liver (mean surface diameter of tumours, 6·13 ± 4·69 mm); animals that had been given AFB₁ in the control diet had 30 ± 16 tumours/liver (mean surface diameter, 4·36 ± 3·16 mm); rats that had been given AFB₁ in the cabbage diet had 13 ± 5 tumours/liver (mean surface diameter, 4·28 ± 2·89 mm). In the Salmonella/ mammalian microsomal test, urine from rats fed AFB₁ with beets caused significantly (P < 0·05) more revertants in Salmonella typhimurium strain TA98 than did urine from rats fed AFB₁ with purified or cabbage diets. The beet- and cabbage-containing diets had no effect on the plasma AFP concentration, hepatic tumorigenesis, or the mutagenicity of urine in rats receiving no AFB₁. The evidence suggests that non-nutrient components of common vegetables may influence the response to chemical carcinogens, and that AFP determinations are useful in the rapid identification of dietary factors that modify carcinogenesis.     

Drug-protein conjugates-VII: Disposition of [3H]-Ethinylestradiol-protein conjugates in the rat

[³H]17α-Ethinylestradiol ([³H]EE₂; 5 μg/kg, 98.5 μCi) was administered to a female rat. After 18 hr less than 0.02% of the dose was present per ml plasma. Approximately 60% of radioactivity present in plasma was irreversibly bound to proteins, as determined by exhaustive solvent extraction and by high performance ion exchange chromatography of proteins after removal of unbound metabolites with activated charcoal. After chronic administration of [³H]EE₂ (5 μg/kg; 2 μCi per day) for 22 days, there was a three- to fourfold accumulation of radioactivity in the plasma, together with an accumulation of radioactivity in the lung, liver, kidney, spleen and brain, compared to animals receiving a single dose. The spleen showed the greatest ( >tenfold) significant (P < 0.001) accumulation of radioactivity. There was a greater increase in radioactivity irreversibly bound to the soluble fraction than to the microsomal fraction of the liver. [³H]EE₂ was conjugated to rat serum proteins by incubation with rat microsomes in vitro. Upon administration to female rats, the [³H]EE₂-rat serum protein conjugate had a small volume of distribution (12.5 ± 0.5 ml), and its plasma concentration declined slowly $\text{(}\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 450 ± 140}\text{min}\text{)}$. Immunization of male New Zealand White rabbits with a chemically synthesized conjugate of 2-hydroxyethinylestradiol (2-OH-EE₂) and human serum albumin produced antibodies which bound EE₂ and 2-OH-EE₂ but not estrone. These data indicate that although reactive metabolite formation represents a minor biotransformation, drug protein conjugates may accumulate during chronic administration.     

A comparative pharmacokinetic study of valpromide and valproic acid after intravenous administration in humans

The pharmacokinetics of valpromide and valproic acid were investigated comparatively in 6 healthy subjects after intravenous administration of the two drugs. Valpromide was very rapidly and almost completely biotransformed to valproic acid (f_m = 81.2 ± 10.5%; mean ± S.D.; n = 6). Relative to valproic acid valpromide has a very short half-life (0.84 ± 0.33 h) a high-clearance value (70 ± 30.5 l/h) and a large volume of distribution (V_β = 75.3 ± 12.7 l). The results of this study showed that there was no significant difference between the biotransformation of valpromide to valproic acid after intravenous administration and that obtained after oral administration of valpromide. Therefore, in humans, valpromide appears to be a prodrug of valproic acid after intravenous as well as oral administration.