Intestinal uptake and biliary excretion of the isoflavone genistein in rats

The intestinal absorption, biliary excretion and metabolism of genistein, a potent and specific protein tyrosine kinase inhibitor that occurs naturally in soy foods, was examined in anesthetized, adult female rats fitted with indwelling biliary cannulas. 4-14C-Genistein, when infused into the duodenum, was rapidly absorbed from the intestine, taken up by the liver and excreted into the bile as its 7-O-beta-glucuronide conjugate. Cumulative recovery of 14C-radioactivity in the bile over a 4-h period was 70-75% of the dose. When genistein was infused into the portal vein, it was also taken up efficiently by the liver, conjugated with glucuronic acid and transported into bile. However, portal blood collected after duodenal infusions of genistein contained mostly genistein 7-O-beta-glucuronide, suggesting that in vivo glucuronidation occurred in the intestinal wall rather than the liver. This was confirmed using everted intestinal sac preparations. Reinfusion of genistein 7-O-beta-glucuronide into the duodenum or into the mid small intestine resulted in its reappearance in the bile, albeit more slowly than when genistein was infused. Over a 4-h collection period, the cumulative recovery of 14C-radioactivity in bile was 27 and 70-75% of the administered dose for duodenal and ileal infusions, respectively. These data indicate that genistein is highly bioavailable in rats and because of its enterohepatic circulation may accumulate within the gastrointestinal tract.     

Ehanced biliary thyroxine excretion in rats treated with pregnenolone-16alpha-carbonitrile

Normal rats were treated with pregnenolone- 16alpha - carbonitrile (PCN) 10 mg/100 g by stomach tube twice daily for 3 days. In these animals the biliary excretion of intravenously injected 125I-thyroxine (T4) was enhanced and the bile: plasma 125I ratio (B/P ratio) and the biliary clearance rate of plasma 125I-T4 was increased. Normal rats were treated with PCN for 3 days and homozygous Gunn rats for 13 days. In both groups PCN enhanced the bile flow and elevated the B/P ratios and the biliary clearance rate of plasma T4 following ip injection of 125I-T4 17 h previously. PCN-treatment had no effect on the fractions of biliary 125I present as T4-glucuronide, T4 and I- in either the normal or Gunn rats. Treatment with PCN for 10 days produced goitres in normal and Gunn rats and in normal rats elevated the serum TSH (bioassay) levels and the 17 h thyroid 131I uptake as well as the serum PB125I concentrations, without affecting stable PBI concentrations. These data indicated increased pituitary TSH release in response to increased peripheral metabolism of thyroid hormone; enhanced hormonal release from the thyroid kept pace with the accelerated peripheral loss.     

The effects of oral diazepam pretreatment on the biliary excretion of sulfobromophthalein in rats

Studies were performed with rats to examine the effects of single, as well as repetitive oral diazepam (DZP) pretreatment on biliary sulfobromophthalein (BSP) excretion rates and on bile flow parameters. One-hour pretreatment of male rats with 150 mg/kg of DZP resulted in about a one-third reduction in the peak biliary excretion rate of BSP (60 mg/kg, iv) and this was associated with a decrease in relative proportions of conjugated BSP in bile. The biliary excretion of preconjugated BSP was unaffected. BSP hepatic uptake and storage were apparently unaffected. In vitro DZP markedly inhibited BSP conjugating activity. In contrast to the above results, when BSP excretion was examined 1 h after the last of five daily oral doses of DZP (150 mg kg-1 day-1), no change in the peak elimination rate of this dye was evident. However, bile flow rates were higher in DZP-treated rats than in controls. When rats were examined 24 h after the last of five daily oral doses of DZP (150 mg/kg), the choleretic response persisted. Further studies showed that the repetitive DZP pretreatment enhanced the bile salt-independent mechanisms of bile formation.     

Granulocyte colony-stimulating factor enhances endotoxin-induced decrease in biliary excretion of the antibiotic cefoperazone in rats

We have recently reported that endotoxin (lipopolysaccharide [LPS]) derived from Klebsiella pneumoniae dramatically decreased the biliary excretion of the beta-lactam antibiotic cefoperazone (CPZ), which is primarily excreted into the bile via the anion transport system, in rats. The present study was designed to investigate the effect of human recombinant granulocyte colony-stimulating factor (G-CSF), which is reported to be beneficial in experimental models of inflammation, on the pharmacokinetics and biliary excretion of CPZ in rats. CPZ (20 mg/kg of body weight) was administered intravenously 2 h after the intravenous injection of LPS (250 microgram/kg). G-CSF was injected subcutaneously at 12 microgram/kg for 3 days and was administered intravenously at a final dose of 50 microgram/kg 1 h before LPS injection. Peripheral blood cell numbers were also measured. LPS dramatically decreased the systemic and biliary clearances of CPZ and the bile flow rate. Pretreatment with G-CSF enhanced these decreases induced by LPS. The total leukocyte numbers were increased in rats pretreated with G-CSF compared to the numbers in the controls, while the total leukocyte numbers were decreased (about 3,000 cells/microliter) by treatment with LPS. Pretreatment with G-CSF produces a deleterious effect against the LPS-induced decrease in biliary secretion of CPZ, and leukocytes play an important role in that mechanism.     

Assessment of biliary excretion of piperacillin-tazobactam in humans

Piperacillin-tazobactam concentrations in serum and bile were measured intraoperatively in 10 patients undergoing cholecystectomy (group 1) and 5 cholecystectomized patients provided with external bile duct drainage (group 2). Each patient received a single intravenous dose of piperacillin at 4 g plus tazobactam at 0.5 g over 30 min. Drug concentrations in both serum and bile were measured by high-performance liquid chromatography. In group 1 patients, serum and bile specimens and gallbladder wall fragments were collected at mean times of 70 and 83 min postinfusion, respectively. The mean concentrations of piperacillin and tazobactam were, respectively, 69.1 +/- 41.5 (standard deviation) and 9.9 +/- 5.1 microg/ml in serum, 630.4 microg/ml (range, 24.8 to 1,194 microg/ml) and 11.8 microg/ml (range, 3.6 to 22 microg/ml) in choledochal bile, 342.3 microg/ml (range, 1.1 to 1,149 microg/ml) and 7.7 microg/ml, (range, 0.2 to 23.1 microg/ml) in gallbladder bile, and 49.3 microg/g (range, 9.7 to 223 microg/g) and 2.9 microg/g (range, 0.1 to 5.9 microg/g) in the gallbladder wall. In group 2 patients, the amounts of drugs recovered in bile drainage obtained over 12 h were 28.4 +/- 18.0 and 1.0 +/- 0.5 mg for piperacillin and tazobactam, respectively. Peak piperacillin and tazobactam concentrations in bile reached 358 +/- 242 and 10.8 +/- 4.2 microg/ml, respectively. Comparison of drug levels in serum and bile suggests an underlying active secretion process for piperacillin elimination into the bile, unlike that of tazobactam. From a therapeutic viewpoint, given the concentrations of tazobactam recorded in bile fluid and tissue, the addition of this beta-lactamase inhibitor to piperacillin therapy might be of interest in the management of biliary tract infections, mostly in patients at risk of mixed aerobic-anaerobic infections due to beta-lactamase-producing organisms.     

Gastric and biliary excretion of meperidine in man

The role and importance of enterogastric secretion in the disposition and elimination of the weak base, meperidine (pKa 8.63), was studied after intravenous administration (50 mg) of the drug to 6 normal volunteers. Continuous collection of the gastric fluid over a 4-hr period demonstrated the establishment of high gastric fluid/plasma concentration ratios for meperidine (mean about 50, range, 10 to 200). However, the total amount of drug recovered, even after correction for incomplete collection, was only a small percentage of the administered dose. Under basal conditions a mean +/- SE of 1.9 +/- 0.3 mg, equivalent to 3.7% of the administered dose, was found in the total gastric aspirate. Stimulation of gastric secretion by subcutaneous injection of betazole (1.5 mg/kg) increased this recovery to 3.6 +/- 0.3 mg (7.2%) primarily due to the increase in gastric volumen output. Aspiration of the gastric fluid in either the basal or stimulated situation had no observable effect upon the plasma concentration/time profile of meperidine whether assessed by the terminal half-life, t 1/2 beta, or the plasma clearance; control values were 3.8 +/- hr and 1,190 +/- 130 ml/min, respectively. In 2 subjects "bile fluid" was also collected for 2.5 hr and found to contain less than 0.2% of the administered dose. Enterosystemic recycling is therefore of minor importance in the disposition and elimination of meperidine in man.     

Comparison of the biliary excretion of the four isomers of bilirubin-IX in Wistar and homozygous Gunn rats

The biliary excretion of the four isomers of bilirubin-IX was studied in Wistar rats (JJ) and homozygous Gunn rats (jj). Synthetic preparations of 14C-labelled pigments were used. 1. After intravenous administration, the alpha-isomer was rapidly excreted in conjugated form in bile of Wistar rats. In Gunn rats excretion was insignificant. In contrast, both rat species promptly excreted the non-alpha-isomers at rates that were comparable with that found for bilirubin-IXalpha in Wistar rats. 2. In normal rats about 16% of the beta- and delta-isomers and at least 50% of the gamma-isomer were excreted as ester conjugates of the injected parent bile pigments. Conjugation of the beta- and delta-isomers had occurred exclusively at the carboxyl groups of pyrrole ring D and C respectively. For bilirubin-IXgamma no preference for any carboxyl group could be established. 3. In homozygous Gunn rats the non-alpha-isomers were apparently excreted chemically unaltered. This suggests that, as for bilirubin-IXalpha, conjugation of the non-alpha-isomers is also deficient in Gunn rats.     

Effect of a bacterial lipopolysaccharide on biliary excretion of a beta-lactam antibiotic, cefoperazone, in rats

Klebsiella pneumoniae O3 lipopolysaccharide (LPS) has been found to dramatically modify the pharmacokinetics of the beta-lactam antibiotic cefazolin in rats. This study investigated the effect of LPS on the biliary excretion of the beta-lactam antibiotic cefoperazone (CPZ) in rats. CPZ is known to be actively secreted into the bile by a carrier-mediated transport system. LPS (250 micrograms/kg of body weight) was infused for 20 to 30 min 2 h before an intravenous administration of CPZ (20 mg/kg). The pharmacokinetic parameters of CPZ were estimated by a noncompartment model. LPS induced a significant decrease in the systemic clearance (by approximately 50%) and an increase in the mean residence time of CPZ. Significant decreases were also seen in the bile flow rate and in the biliary recovery of unchanged CPZ in the LPS-treated rats. LPS tended to increase the proportion of urinary excretion of CPZ. LPS significantly decreased the biliary clearance (by approximately 55%) and renal clearance (by approximately 35%) of CPZ. However, no changes in the volume of distribution at steady state for CPZ were observed between the treatment groups. Our findings suggest that LPS induces changes in the pharmacokinetics of CPZ as a result of changes occurring in the biliary secretory system.     

Iodipamide kinetics: capacity-limited biliary excretion with simultaneous pseudo-first-order renal excretion

Iodipamide was infused into three dogs with bile fistulas to achieve various steady-state blood levels. When using ultracentrifugation techniques, iodipamide was found to be highly bound to plasma protein. The total blood clearance was low relative to hepatic blood flow. For either the whole blood concentration or the unbound concentration of iodipamide, the biliary excretion was shown to be capacity limited with a transport maximum, Tm, of approximately 1.0mumole/kg/min. The steady-state renal excretion rate, plotted against the whole blood concentration of iodipamide, resulted in a concave ascending curve, which could lead to the false conclusion that iodipamide was undergoing active renal tubular reabsorption. However, when corrected for plasma protein binding, a linear relationship was obtained, suggesting that the renal excretion of iodipamide is a pseudo-first-order process. The Michaelis-Menten parameters for the extrarenal elimination, when calculated using the whole blood concentration of iodipamide, led to a similar discrepancy compared to the parameter estimates obtained from biliary excretion rate data. This discrepancy can be eliminated when one uses the unbound concentration of iodipamide in the parameter estimates.     

Role of metabolism in the biliary excretion of methadone metabolites

1. The effects of six local anaesthetics have been studied on the activities of soluble phospholipases A2 (EC 3.1.1.4) and lysophospholipase (EC 3.1.1.5). 2. Phospholipase A2 activity in human seminal plasma towards sonicated radioactively-labelled phosphatidylethanolamine was slightly stimulated a low and inhibited at high concentrations of all anaesthetic compounds employed. The order of decreasing potency was chlorpromazine, dibucaine, tetracaine, lidocaine, cocaine and procaine. In line with previous findings, the mode of inhibition was seen to be competitive with respect to Ca2+. 3. Phospholipase A2 activity in crude venom of Crotalus adamanteus was not affected or slightly stimulated by local anaesthetics up to 10(-2) M concentrations, when egg yolk was used as substrate. However, with sonicated radioactively-labelled phosphatidylcholine or phosphatidylethanolamine as substrate, stimulation of phospholipase activity was seen with all local anaesthetics up to 10(-2) M, the order of decreasing potency again being chlorpromazine, dibucaine, tetracaine, lidocaine, cocaine and procaine. The mode of stimulation was seen to be un-competitive with respect to substrate and probably independent of any involvement of Ca2+. 4. As in seminal plasma phospholipase A2, the activity in crude Naja naja venom towards sonicated radioactively labelled phosphatidylcholine was stimulated at low and inhibited at high concentrations of dibucaine and chloropromazine, for example. The mode of inhibition was seen to be competitive with respect to Ca2+, whereas stimulation by the anaesthetic drugs was independent of Ca2+. Binding between drug and enzyme was demonstrated by equilibration filtration of purified phospholipase A2 of Naja naja venom through a Sephadex G 25-fine column, previously equilibrated with 0.5 mM radioactively labelled chlorpromazine. 5. Lysophospholipase activity in rat liver cytosol towards radioactively labelled lysophosphatidylcholine was inhibited by all local anaesthetics used; the order of decreasing potency was chlorpromazine, dibucaine, tetracaine, cocaine, lidocaine and procaine. The inhibition was un-competitive with respect to substrate. 6. The inhibitory and stimulatory potencies of the local anaesthetics employed closely parallel their lipid solubilities and anaesthetic potencies.     

Biliary excretion of cobalt in rats

The excretion of 58Co2+ via bile, urine and intestinal wall after intravenous administration of 58CoCl2 in two doses (177 and 1770 micrograms of Co2+ per kg B. Wt.) was studied in rats. The cumulative biliary excretion reached 24 hours after administration of lower dose 2.67 +/- 1.98% and higher dose 7.33 (4.6-10.9) % of the amount given. The highest excretion rate of 58Co was detected between 10 and 30 minutes after administration. After administration of higher dose of 58Co the lower urinary excretion was observed [73.6 +/- 4.0% resp. 47.9% (45.5-52.5)] of the amount given. There were no differences between both doses studied in the excretion of 58Co via the wall of gastrointestinal tract.     

The effects of castration and treatment with testosterone on the biliary excretion of (3H)aldosterone in rats

The rate of excretion of aldosterone radiometabolites into the bile duct cannulation, and the intravenous injection of (3H)aldosterone, was demonstrated to be markedly increased in male rats following castration. In 1 h, 72% of the injected 3H-radioactivity was excreted in the bile of castrated male rats compared with 26% in the intact male control rats. Castration of the males led to the increased biliary excretion of aldosterone metabolites and the elimination of the sex-dependence of this process in rats. The ovariectomy of female rats did not substantially increase the rate of excretion of aldosterone metabolites via the bile. Castrated male rats treated with testosterone excreted aldosterone metabolites into the bile at a slower rate. A similar treatment of ovariectomized female rats with testosterone also significantly slowed the rate of biliary excretion of the aldosterone metabolites. These findings suggest that the presence of androgens plays an important role in regulating the routes of hepatic metabolism of aldosterone and the rates of clearance of aldosterone and its metabolites from the plasma into the bile of rats.     

Multispecific organic anion transporter is responsible for the biliary excretion of the camptothecin derivative irinotecan and its metabolites in rats

Irinotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxycamptothecin (CPT-11), is a potent anticancer drug that is increasingly used in chemotherapy. A frequent limiting side effect involves gastrointestinal toxicity (diarrhea), which is thought to be related to the biliary excretion of CPT-11 and its metabolites. Accordingly, the biliary excretion mechanisms for both the lactone and carboxylate forms of CPT-11 and its metabolites, SN-38 and its glucuronide (SN38-Glu), were investigated using Sprague-Dawley (SD) rats and Eisai hyperbilirubinemic rats (EHBR), with the latter being mutant rats with a genetic deficiency of the canalicular multispecific organic anion transporter. After i.v. administration of CPT-11, the biliary excretion clearance, defined as the biliary excretion rate normalized to the hepatic concentration, of both the lactone and carboxylate forms of SN38-Glu was much lower in EHBR. The biliary excretion clearance for the carboxylate form of both CPT-11 and SN-38 was also substantially smaller in EHBR and showed marked saturation with increasing dose only in SD rats. On the other hand, the biliary excretion clearance for the lactone forms of CPT-11 and SN-38 showed only a minimal difference in EHBR, compared with SD rats. These results suggest that, for the carboxylate form of CPT-11 and SN-38 and the carboxylate and lactone forms of SN38-Glu, there exists a specific transport system at the bile canalicular membrane that is deficient in EHBR. To confirm this hypothesis, the uptake of these substrates by isolated hepatic canalicular membrane vesicles (CMV) was examined. ATP-dependence was clearly observed for the uptake of these four compounds by CMV prepared from SD rats but not by CMV from EHBR. In addition, the compounds inhibited the ATP-dependent uptake of S-(2,4-dinitrophenyl) glutathione by CMV from SD rats, in a concentration-dependent manner. These results suggest that the biliary excretion of the carboxylate forms of CPT-11 and SN-38 and the carboxylate and lactone forms of SN38-Glu is mediated by the multispecific organic anion transporter, which is deficient in EHBR.     

Improvement of biliary excretion of ioglycamide by pretreatment with phenobarbital

The influence of a phenobarbital pretreatment on the distribution and biliary excretion of Ioglycamide was studied in 6 experiments in the anaesthetized minipig. The phenobarbital pretreatment led to a significant increase of the biliary transportmaximum and the biliary concentration of Ioglycamide. A detailed analysis suggests a phenobarbital induced stimulation of the hepatocellular excretion. The applicability of a pretreatment with phenobarbital in order to improve the opacification of the biliary system during x-ray-examinations with Ioglycamide is discussed.     

Urinary kallikrein excretion in pregnant adrenalectomized rats

The mechanisms responsible for the increase of the urinary kallikrein activity (UKA) during pregnancy is still unknown. Since aldosterone has been described as one of the stimulatory factor of UKA, and this hormone is considerably elevated in normal pregnancy it is feasible to postulate that it might be involved in the process. A preliminary approach to solve the role of the mineralocorticoid was to investigate the effect of the adrenalectomy upon UKA, of pregnant rats. UKA activity and blood pressure (BP) were measured at weekly intervals in four groups of rats: pregnant-adrenalectomized (P-ADX); pregnant-sham operated (P-C); non pregnant-adrenalectomized (NP-ADX) and non pregnant-sham operated (NP-C). In addition serum aldosterone levels in pregnant rats were determined. All the groups were maintained in similar conditions drinking 1% NaCl solution. The increase in UKA was not detected in P-C, as observed in normal pregnant rats drinking tap water, indicating that a high NaCl intake prevents the rise in UKA during gestation. However, P-C rats had higher UKA than P-ADX on day 14 of pregnancy (p < 0,05). The lowest level of UKA was found in NP-ADX. In NP-C and NP-ADX BP rose progressively throughout the experiment. BP in P-ADX rats during pregnancy and on day 7 of post partum was significantly lower than in P-C rats (p < 0,01-0,02) but in both pregnant groups it decreased significantly before parturition (p < 0,02) increasing at post-partum. Serum aldosterone levels on days 14 ans 21 of gestation, showed higher values in P-C than in P-ADX (p < 0,02-0,005). The results provide support to the assumption that adrenal gland has a regulatory action on UKA during pregnancy and that aldosterone can be one of the main factors involved.     

Bile flow in a mutant Sprague-Dawley rat with defective biliary excretion of glutathione

The Eisai hyperbilirubinemic rat is a mutant strain of Sprague-Dawley origin with hereditary defects in the biliary excretion of bilirubin glucuronide, glutathione, and several other organic anions. The correlation between bile flow and bile acid excretion rates during taurocholate infusion revealed that bile acid-independent flow was smaller in the mutant than in intact Sprague-Dawley rats (19.3 vs 56.0 microliters/kg per min), while bile acid-dependent flow was similar. The correlation between bile flow and glutathione excretion rates in Sprague-Dawley rats with modified hepatic glutathione levels revealed that a certain portion of bile flow was proportional to the biliary excretion of glutathione, with a coefficient of 551 bile per 1 mol glutathione. One-third of bile acid-independent bile flow in intact Sprague-Dawley rats was accounted for by glutathione osmosis, which feature was absent in the mutant rats.     

Chronokinetics of active biliary ampicillin secretion in rats

To estimate the functional maturity of the phagocytic defence in neonatal calves, we analyzed the characteristics of blood phagocytes from calves (n = 10) 1 h post partum (p.p.) and 4 h p.p. At 1 h p.p., all calves were colostrum-deprived, while 5 calves had received colostrum before the 4 h p.p. sampling. The results were compared to those obtained from 3-9-week-old calves (n = 10). Phagocytic and oxidative burst activity of polymorphonuclear leukocytes (PMNL) and monocytes were determined in whole blood and separately analyzed by flow cytometry. In neonates prior to colostrum ingestion (1 h p.p.), phagocytic activity of PMNL against non-preopsonized E. coli was lower when compared to PMNL of 3-9-week-old calves. Opsonization of bacteria with pooled plasma from adult animals only partially restituted this lower PMNL phagocytic activity, indicating that humoral as well as cellular aspects of PMNL phagocytosis are altered in neonatal calves. In contrast to PMNL, monocytes of neonates exhibited an enhanced phagocytic activity. The oxidative burst activity of PMNL, as well as of monocytes was higher in newborn calves. During the first 4 h of life, the activities of blood phagocytes changed. Colostrum ingestion was accompanied by an increase in the percentage of phagocytizing PMNL and monocytes. This increase was absent in colostrum-deprived calves. In contrast, the oxidative burst activity of phagocytes decreased with age. In monocytes, the decrease of oxidative burst activity was only observed in colostrum-fed calves. In conclusion, some blood phagocyte functions in calves were found to be immature at birth, but these functions are presumably compensated by high absolute PMNL numbers and by other the more active mechanisms.