Sequential changes in redox status and nitric oxide synthases expression in the liver after bile duct ligation.

Bile duct ligation (BDL) in rats induces portal fibrosis. This process has been linked to changes in the oxidative state of the hepatic cells and in the production of nitric oxide. Our objective was to find possible temporal connections between hepatic redox state, NO synthesis and liver injury. In this work we have characterized hepatic lesions 17 and 31 days after BDL and determined changes in hepatic function, oxidative state, and NO production. We have also analyzed the expression and localization of inducible NO synthase (NOS2) and constitutive NO synthase (NOS3). After 17 and 31 days from ligature, lipid peroxidation is increased and both plasma concentration and biliary excretion of nitrite+nitrate are rised. 17 days after BDL both NOS2 and NOS3 are expressed intensely and in the same regions. 31 days after BDL, the expression of NOS2 remains elevated and is localized mostly in preserved hepatocytes in portal areas and in neighborhoods of centrolobulillar vein. NOS3 is localized in vascular regions of portal spaces and centrolobulillar veins and in preserved sinusoids and although its expression is greater than in control animals (34%), it is clearly lower (50%) than 17 days after BDL. The time after BDL is crucial in the study of NO production, intrahepatic localization of NOS isoforms expression, and cell type involved, since all these parameters change with time. BDL-induced, peroxidation and fibrosis are not ligated by a cause-effect relationship, but rather they both seem to be the consequence of common inductors.

Effects of melatonin on fuel utilization in exercised rats: role of nitric oxide and growth hormone.

We have previously reported that melatonin modifies carbohydrate and lipid utilization in exercised rats, maintaining glycemia and reducing plasma and liver lactate and plasma beta-hydroxybutyrate. This study was undertaken to determine whether effects on fuel metabolism were related to changes in nitric oxide (NO) production or growth hormone (GH) secretion. Male Wistar rats received melatonin i.p. at a dose of 0.5 mg/kg body weight 30 min before being exercised to exhaustion on a treadmill at a speed of 24 m/min and a 12% slope. Melatonin ameliorated the decrease in plasma glucose and the increase in plasma urea, free fatty acid, beta-hydroxybutyrate, and nitrite induced by exercise. Melatonin-treated exercised rats had significantly elevated liver glycogen content and hepatic tissue showed a lowered expression of both inducible and constitutive NO synthase (iNOS and cNOS). Administration of the NO inhibitor NG-nitro-L-arginine (L-NAME) to exercised rats caused a significant reduction in plasma nitrite, but liver glycogen and biochemical parameters in blood did not significantly differ from untreated exercised animals, indicating the absence of a direct association between melatonin effects on fuel metabolism and NO levels. Although results of treatment with pyridostigmine, a cholinergic agonist drug that stimulates GH release, partially differed from that of melatonin, modulation of GH secretion could play a role in the metabolic actions of the hormone because effects of melatonin on exercised rats were almost completely blocked by simultaneous administration of L-NAME.

Role of prostanoids and nitric oxide inhibition in rats with experimental hepatic fibrosis.

Nitric oxide (NO) and prostaglandins have been proposed as vasodilator substances involved in peripheral vasodilatation characteristic of the liver cirrhosis. A link between NO and prostanoids has been suggested. The present study investigated the effect of simultaneous blockade of both, NO synthase (NOS) and cyclooxigenase (COX) in sham-operated (SO), or rats with bile-duct ligation (BDL) in the development of liver fibrosis. Animals were distributed in two groups SO (n=15) or BDL (n=15). Treatments (5 days) started three weeks after surgical procedure. Both, SO and BDL animals were treated with indomethacin (INDO) (5 mg/kg/day) alone, with NG-nitro-L-arginine-methyl-ester (NAME) (4 mg/kg/day) alone or with INDO and NAME combination at the same doses. At the end of follow-up body weight, packed cell volume, mean arterial blood pressure (MAP) and heart rate were measured. Liver tissue was processed for histological studies. In this study, BDL animals showed a decreased MAP. Treatment with L-NAME in BDL rats increased MAP. The chronic COX inhibition alone did not play an important role in the haemodynamic changes. The BDL produced a loss of hepatic structure, with ductular metaplasia that occupied the greater part of the hepatic parenchyma. Also, an important degree of fibrosis was observed. Both NO and PG synthesis inhibitors, alone or in combination, induced enhancing collagen fiber deposition in the hepatic parenchyma. These findings support the notion that the interaction between the NOS and COX pathways should be relevant in hepatic cirrhosis in which both NOS and COX are induced.

Correlation of high levels of hyaluronan and cytokines (IL-1beta, IL-6, and TGF-beta) in ascitic fluid of cirrhotic patients.

Our objective was to investigate the relationship between endotoxin and hyaluronan synthesis and release in serum and ascitic fluid from cirrhotic patients. We studied hyaluronan, endotoxin, albumin, and creatinine levels in ascitic fluid and plasma and cytokine levels (IL-1beta, IL-6, TGF-beta) in ascitic fluid. TGF-beta, IL-6, and IL-1beta correlation analyses indicated a strong dependence of the production of these cytokines on endotoxin levels. Correlation analyses for TGF-beta and IL-6 indicated a strong dependence of the production of hyaluronan on cytokine levels and, to a lesser extent, on IL-1beta levels. Hyaluronan analysis indicated that a certain glycosaminoglycan level is required in ascites before its appearance in plasma. Our results disclosed elevated plasma hyaluronan concentrations. The simultaneous increased hyaluronan levels in ascitic fluid do not seem to be derived from the systemic circulation. In conclusion, the high hyaluronan-ascites/hyaluronan-plasma ratio suggests an intrinsic hyaluronan production from peritoneal cells induced by endotoxins.

Effects of chronic nitric oxide activation or inhibition on early hepatic fibrosis in rats with bile duct ligation.

Hepatic fibrosis or increased liver collagen contents drive functional abnormalities that, when extensive, may be life threatening. The purpose of this study was to assess the effects of the chronic stimulation or inhibition of nitric oxide synthesis in rats with hepatic fibrosis induced by permanent common bile duct ligation (3 weeks) and the role of expression of the different nitric oxide synthase isoforms. Bile duct ligation led to an important accumulation of collagen in the hepatic parenchyma, as shown both histologically and by the hydroxyproline contents of livers. Bilirubin and serum enzyme activities (measured as markers of cholestasis) increased several-fold after bile duct ligation. The area of fibrotic tissue, liver hydroxyproline content and serum markers of cholestasis were clearly related in obstructed rats. The absence of modifications in haemodynamic parameters excludes circulatory changes from being responsible for the development of liver alterations. In animals treated with NG-nitro-L-arginine methyl ester (L-NAME) the area of fibrosis was similar to that of untreated animals, the signs of cholestasis and cellular injury being more evident. In rats treated with L-arginine the area of fibrosis was almost three times larger than that found in bile duct ligated rats and in L-NAME-treated bile duct ligated rats, although the observed biochemical changes were similar to those seen in rats treated with L-NAME. Our results with inducible nitric oxide synthase, obtained by Western blots and immunohistochemistry, indicate a greater expression of the inducible enzyme in bile duct ligated and L-arginine-treated animals and a lower expression in the L-NAME and control groups. Constitutive nitric oxide synthase expression, obtained by Western blots, was very similar in all groups, except for the L-arginine-treated rats in which it was lower. These results suggest that nitric oxide production may be a key factor in the development of fibrosis in bile duct ligated rats. They also support the hypothesis of a dual role for nitric oxide; one beneficial, mediated by its circulatory effects, and the second negative, through its local toxic effects.

Increased nitric oxide synthesis and inducible nitric oxide synthase expression in patients with alcoholic and non-alcoholic liver cirrhosis.

1. The synthesis and release of nitric oxide may play a role in the pathogenesis of peripheral vasodilatation and hyperdynamic circulation observed in liver cirrhosis. In this work, we analysed the synthesis of nitric oxide by the lympho-mononuclear cells of peripheral blood from patients with chronic alcoholic and non-alcoholic liver disease and we identified the isoform of nitric oxide synthase involved in the increased nitric oxide synthesis. 2. Patients were classified following clinical and histological criteria in non-alcoholic cirrhotic, alcoholic cirrhotic and non-cirrhotic chronic liver disease. We studied clinical and analytical characteristics, haemodynamic parameters and endotoxin levels in these patients. 3. Cirrhotic patients showed an increase of cardiac output and a decrease of peripheral vascular resistance. These patients had higher levels of plasma endotoxin than those observed in the control group. N omega-Nitro-L-arginine methyl ester (L-NAME)-inhibitable nitrite production from mononuclear lymphocyte cells was higher in patients than in the control group, the highest levels being in non-alcoholic cirrhotic patients, and the lowest levels in patients with non-cirrhotic alcoholic liver disease. 4. Immunocytochemistry studies revealed a positive immunoreactivity for the inducible isoform of nitric oxide synthase in lympho-mononuclear cells that was more evident in non-alcoholic than in alcoholic cirrhotic patients. By Northern blot, inducible nitric oxide synthase mRNA expression was observed only in lymphomononuclear cells from non-alcoholic cirrhotic patients. 5. Our patients show a correlation between nitric oxide synthesis, endotoxin levels and haemodynamic parameters. 6. These findings indicate that lympho-mononuclear cell stimulation may play a role in elevated nitric oxide production in hepatic cirrhosis. Thus, this increased nitric oxide synthesis could be implicated in the pathogenesis of the haemodynamic disturbances frequently found in cirrhotic patients. This increase seems to be induced, at least in part, by activation of an inducible isoform of nitric oxide synthase.

Acid-base disturbances in the rabbit during experimental hepatic parasitosis.

Acid-base disturbances were examined during experimentally induced infection in the rabbit with Eimeria stiedai, a parasite that profoundly modifies liver morphology and physiology, resulting in anatomical and functional alterations similar to those appearing in different human hepatic diseases. Over 28 days of infection, bicarbonate and lactate concentrations, partial pressures of O2 and CO2, and pH values were determined in the blood and bile of infected animals and compared with the values obtained in noninfected rabbits. The plasma activity of several liver-indicator enzymes was also evaluated. Under our experimental conditions we observed an uncompensated metabolic acidosis that developed with elevated levels of lactate and reduced concentrations of bicarbonate in blood and bile and tended to be compensated by respiratory and biliary mechanisms.

Five-year follow-up evaluation of the noncemented press-fit titanium hip-joint endoprosthesis.

A series of 260 noncemented total hip arthroplasties with a titanium alloy stem and fixation by the Zweymüller press-fit and an Endler polyethylene threaded cup was reviewed in detail. The minimum follow-up period was 48 months and the maximum 72 months, with an average of 60 months. A scale from zero to five points was applied to evaluate pain, mobility, and motion for a total possible accumulation of 15 points. The global results of the different etiologic groups (arthrosis, femoral head necrosis, rheumatoid arthritis, and subcapital hip fractures) have been very good and good (12-15 points) in 67.5% of the cases and fairly good and bad in 32.3%. These results have been better in femoral head necrosis than in arthrosis or rheumatoid arthritis, but not as good in subcapital hip fractures. The age groups below 60 had better results than the above 60 groups. The Singh index higher than 3 was correlated with better-than-average results. The polyethylene cup migrated horizontally (more than 4 mm) in 7.6% of the cases and vertically (more than 5 mm) in 10%. The non-evolutionary cortical remodelation of the femur does not influence the results. Prosthetic stem sinking less than 4 mm has been found in 62% of the cases, from 4 to 9 mm in 21%, and greater than 9 mm in 6%. No alterations with clinical consequences attributable to stress-shielding have been detected.

Inhibition of biliary lipid and protein secretion by cyclosporine A in the rat.

We investigated the effect of cyclosporine A (CyA) administered as a single i.v. dose of 20 and 40 mg/kg body wt, on biliary secretion of cholesterol, phospholipid, bile acid, and lysosomal marker and canalicular plasma membrane marker enzymes in anaesthetized Wistar rats. CyA reduced the concentration and biliary secretion of cholesterol, phospholipid and bile acid to a considerable extent; the inhibitory effect of CyA on the biliary secretion of phospholipid and bile acid was greater than that on cholesterol. The biliary outputs of acid phosphatase (AcP) and gamma-glutamyltransferase (gamma-GT) were also diminished by the drug, all these effects being dose-dependent. Maximum decreases in bile acid secretion were observed 10 min after administration, whereas those of cholesterol and phospholipid were delayed. Bile acid concentrations and secretion returned to pretest values at 30-50 min after CyA injection whereas those of cholesterol and phospholipid remained significantly reduced at this time point. The greater inhibitory effect of CyA on the biliary outputs of phospholipid and bile acid relative to cholesterol secretion together with the asynchronous fall and recovery of bile acid, cholesterol and phospholipid concentrations and secretion alter the cholesterol/bile acid, phospholipid/bile acid and cholesterol/phospholipid molar ratios as well as the lithogenic index, thus suggesting that CyA would uncouple biliary lipid secretion from bile acid secretion. Since under physiological conditions biliary lipid and gamma-GT secretion is related to and dependent upon bile acid secretion, we propose that the CyA-induced inhibition on lipid and gamma-GT secretion is, at least partly, secondary to the fall in bile acid output caused by the drug. However, since CyA inhibits secretory processes independent of the hepatobiliary flux of bile acid, such as the exocytic discharge of AcP, and because it also uncouples biliary lipid from bile acid secretion, other mechanisms and factors involved in lipid and protein secretion (such as intracellular transport, canalicular membrane fluidity and/or intracanalicular events) might also be altered by this drug.

Inhibition of hepatocytary vesicular transport by cyclosporin A in the rat: relationship with cholestasis and hyperbilirubinemia.

In an attempt to understand the hepatotoxicity associated with immunosuppressive therapy with cyclosporin A, we investigated the effects of acute cyclosporin A administration on biliary secretion, serum bile acid and bilirubin levels and the histological changes in the hepatic parenchyma in anesthetized male Wistar rats. The animals were divided into three experimental groups that received equal volumes (1 ml, intravenously) of physiological saline (controls), cyclosporin A vehicle (a fat emulsion, Intralipid, mixed with absolute ethanol) or cyclosporin A dissolved in the aforementioned mixture. In another series of assays, horseradish peroxidase was coinjected with cyclosporin A vehicle or with the solution containing cyclosporin A. Only after cyclosporin A administration was an immediate inhibition in bile flow and in the biliary concentrations and secretion of bile acids and bilirubin found. In addition, a delay in the peak time of the appearance of horseradish peroxidase together with a reduction in the biliary excretion rate and in the total amount of horseradish peroxidase excreted were observed during cholestasis. At 40 to 50 min after drug administration, all biliary parameters evaluated had returned to the pretest values. The relationship between bile flow and bile acid secretion showed that cyclosporin A-induced cholestasis is related to a decrease of both the bile acid-dependent and bile acid-independent fractions of bile flow. At the end of the cyclosporin A assays, the serum bile acid, total bilirubin and conjugated bilirubin concentrations were greater than those observed in the controls and Intralipid-treated animals. These effects were dose-dependent. Light microscopy and transmission electron microscopy studies did not reveal architectural hepatic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics, hepatic biotransformation and biliary and urinary excretion of bromosulfophthalein (BSP) in an experimental liver disease mimicking biliary cirrhosis.

We studied the hepatic handling of bromosulfophthalein in healthy rabbits with hepatic coccidiosis 28 days after an experimental infection with sporulated oocysts of Eimeria stiedai, an experimental model of liver disease histopathologically resembling primary biliary cirrhosis in man. A pharmacokinetic study of the results was performed following a multicompartmental model with 7 transfer constants to describe the physiological disposition of the dye. The study showed that the plasma disappearance, distribution volume (Vi), hepatic biotransformation and the biliary and urinary elimination of conjugated (BSPc) and unconjugated (BSPu) bromosulfophthalein were markedly altered. Whereas Vi and urinary excretion of the dye were significantly increased, the hepatic clearance, biotransformation and biliary excretion of BSPc and BSPu were drastically reduced in infected rabbits. Satisfactory agreement was obtained between the experimental and estimated data, particularly those relating to biotransformation clearance and biliary and urinary excretion of the dye. These results demonstrate that severe liver disease in rabbits with histopathological liver alterations resembling several hepatic dysfunctions in man markedly reduce hepatic uptake, metabolism and biliary excretion of a xenobiotic such as BSP.

Choleretic mechanism and effects of cyclobutyrol in the rat: dose-response relationship.

Although there is general agreement on the hydrocholeretic properties of the so-called "synthetic choleretics" on biliary secretion, related simply to the kinetics of excretion, recent studies suggest that some of these drugs also have a pharmacodynamic effect; mainly, stimulation of bile acid secretion. In the present work, we studied the biliary response to different doses of cyclobutyrol (CB) in order to determine whether this agent stimulates the secretion of bile acids and to establish the relationships between dose and the choleretic effects in anaesthetized rats. Biliary bile flow, sodium, potassium, chloride and bicarbonate outputs were found to be increased and bile acid concentrations reduced in a dose-dependent fashion after 0.40, 0.54, 0.80, 1.08 and 2.16 mmol/kg b.wt. of CB administration. All assayed doses had no effect on the bile acids secretion rate. These findings suggest that a) CB-induced choleresis is unrelated to bile acids; b) CB and bile acids do not compete for the hepatobiliar transport mechanisms, despite the anionic character of both compounds, and c) in the rat the active mechanisms involved in the biliary elimination of CB are not saturated even at the large doses employed.

Inhibition of biliary cholesterol and phospholipid secretion during cyclobutyrol-induced hydrocholeresis.

The effects of sodium cyclobutyrate, a synthetic hydrocholeretic drug, on biliary lipid secretion and on the biliary outputs of several plasma-membrane enzymes were investigated in anaesthetized rats. Administration of a single oral dose of cyclobutyrol (0.72 mmol/kg body wt.) reduced biliary concentration and output of cholesterol and phospholipid. However, bile acid secretion was not significantly modified. This uncoupling effect of lipid secretion remained even when the choleretic response to the drug had ceased. It additionally led to a statistically significant decrease in the cholesterol/bile acid and phospholipid/bile acid molar ratios and in the lithogenic index of the bile. The biliary outputs of the plasma-membrane enzymes alkaline phosphatase and gamma-glutamyltransferase were markedly reduced by the drug. When cyclobutyrol was administered to rats which had been previously fed with a high-cholesterol diet, the effects of cyclobutyrol persisted, but were less marked. Our results demonstrate that the bile acid-independent choleresis induced by cyclobutyrol (related to its pharmacokinetic effect) is accompanied by a pharmacodynamic action that selectively reduces the secretion of biliary lipids. This is due to an uncoupling of the secretion of cholesterol and phospholipids from that of bile acids. Possible explanations for the biliary response to cyclobutyrol are discussed.

Cholestasis in the rat by means of intravenous administration of cyclosporine vehicle, Cremophor EL.

The effect of cyclosporine vehicle, Cremophor EL, on bile flow and biliary bile acids and bilirubin output was studied in anesthetized male Wistar rats. Intravenous administration of Cremophor EL or castor oil as a single bolus reduced bile flow and the biliary output of bile acids and bilirubin. The Cremophor EL-induced cholestasis was an immediate and reversible phenomenon, since at 30-35 min after drug injection all parameters evaluated had returned to control values. A slight increase in serum bilirubin concentrations was observed. Our data indicate that the observed cholestasis is related to a reduction in both bile acid-dependent and bile acid-independent bile flow, probably due to a transitory hepatotoxic effect of Cremophor EL. We conclude that the clinically used vehicle for i.v. administration of cyclosporine, Cremophor EL, has adverse effects on hepatobiliary physiology in the rat and suggest that an alternative vehicle should be used.

Inhibition of fibrinolysis by cellular glutathione depletion in the rabbit.

The effect of cellular glutathione depletion on fibrinolytic activity in the arterial wall and on the levels of components of the plasma fibrinolytic system was studied in rabbits. Intraperitoneal administration of buthionine sulphoximine (4.5 mmol/kg body wt), an inhibitor of gamma-glutamyl cysteine synthetase, induced a significant reduction in liver glutathione concentrations with a peak decrease of 51% at 7 hours and a progressive return to normal values. The glutathione concentration in aortic tissue was also significantly reduced 7 h after administration of the depleting agent. Fibrinolytic activity in the arterial wall was inhibited following buthionine sulphoximine administration and only reappeared at 24 hours postinjection. Diethyl maleate administration (3.2 mmol/kg body wt i.p.) also depleted liver and aortic glutathione and inhibited fibrinolysis in the arterial wall. Treatment with both glutathione-depleting agents induced a significant reduction in the functional activity of tissue plasminogen activator (t-PA) (-61% and -27% respectively for buthionine sulphoximine or diethyl maleate) and a significant increase in that of plasminogen activator-inhibitor (PAI) (+61% and +27% respectively), while alpha-2-antiplasmin activity was not modified. Our data suggest a modulatory role of glutathione in the release and/or clearance of the components of the fibrinolytic system in the rabbit.

Influence of bile acids on the biliary transport maximum of phenolsulfonphthalein in the rat.

1. The effect of changes in bile acid secretion induced by cholestyramine treatment or taurocholate infusion on the biliary transport maximum (Tm) of phenolsulfonphthalein (PSP) was studied in Wistar rats. 2. Five hours after oral administration of cholestyramine (1.5 g/kg bodyweight) the biliary output of bile acids decreased to 51% and bile flow to 76% of control values. The percentage of conjugated and unconjugated PSP excreted into bile and the Tm of the dye were not significantly modified by cholestyramine pretreatment. 3. Administration of sodium taurocholate at increasing rates (60-480 nmol/100 g bodyweight per min) enhanced bile flow and the biliary output of bile acids in a linear dose-related fashion. The Tm of PSP increased progressively until a maximum of 29% above the control values was reached at a taurocholate dose of 240 nmol/100 g bodyweight per min). The enhancement corresponded mainly to the unconjugated dye, the excretion of conjugated PSP not being significantly modified by the infusion of the bile acid. 4. The results indicate that bile acids can influence to some extent biliary excretion of PSP in the rat, although this component is of minor importance at low bile acid secretory rates.

Evidence for the presence of carbonic anhydrase in the plasma membrane of rat hepatocytes.

The cellular distribution of carbonic anhydrase is a key characteristic for the role of the enzyme in cell function. In several epithelia involved in bicarbonate transport this enzyme is located in the plasma membrane. Because bicarbonate secretion is an important mechanism in bile formation by the liver, we investigated the presence of carbonic anhydrase activity in isolated plasma membranes from rat hepatocytes. Carbonic anhydrase activity was enriched 1.79-fold in plasma membrane preparations. This activity was inhibited by acetazolamide and activated by Triton X-100, but was insensitive to Cl- or CNO-. It is highly unlikely that the low contamination of cytoplasm and intracellular membranes could account for the presence of carbonic anhydrase activity in plasma membrane preparations. Moreover, the results from resuspension/washing of plasma membrane fractions in ionic media suggest an absence of soluble carbonic anhydrase adsorption upon plasma membrane. Accordingly, the present findings provide strong evidence for the presence of carbonic anhydrase in the plasma membrane of rat hepatocytes.

Impairment of sulfobromophthalein biliary excretion and inhibition of glutathione S-transferase activity induced by perhexiline maleate in rats.

The effect of the antianginal agent perhexiline maleate (160 mg/kg i.g., daily for 4 days) on the biliary excretion of sulfobromophthalein (BSP) and BSP-glutathione and the hepatic activity of glutathione S-transferases was investigated in Wistar rats. Perhexiline maleate caused a significant reduction in the maximal biliary excretion of BSP (-28%). The decrease corresponded to a lowered excretion of the conjugated dye whereas the excretion of the parent compound did not change significantly. Administration of the drug caused no effect on the maximal biliary excretion of infused BSP-glutathione. Liver glutathione concentrations were similar in control and treated rats. Perhexiline maleate significantly reduced liver glutathione S-transferase activities toward BSP (-25%), 3,4-dichloronitrobenzene (DCNB) (-21%) and 1-chloro-3,4-dinitrobenzene (DNCB) (-27%). Kinetic studies of the enzyme in liver cytosol showed that perhexiline maleate induced an uncompetitive inhibition for the BSP substrate with a reduced Vmax and Km. The results indicate that the reduction in glutathione S-transferase activity plays an important role as a factor determining the impairment in the hepatobiliary transport of BSP caused by perhexiline maleate.

Impairment of bromosulfophthalein hepatic transport and cholestasis induced by diethyl maleate in the rabbit.

The present study was designed to investigate the effect of hepatic glutathione depletion induced by intraperitoneal administration of diethyl maleate (DEM) on the maximum biliary transport (Tm) and on the biliary excretion of bromosulfophthalein (BSP) in anaesthetized rabbits when the dye was perfused endovenously at doses exceeding Tm. The Tm of total BSP (BSPt) and that of conjugated BSP (BSPc) were significantly reduced after DEM administration whereas that of unconjugated BSP (BSPu) was markedly increased. A reduction in the biliary excretion of BSPt and BSPc, in the percentage of BSPc, in the cumulative excretion of BSPt and in the percent-dose recovery were also observed. However, no change in hepatic glutathione S-transferase activity was noted after DEM. The cholestasis observed following DEM administration coursed with falls in the biliary secretion of sodium, chloride and bicarbonate.

Phenolsulphonphthalein conjugation and biliary excretion in the rat: influence of phenobarbital and 3-methylcholanthrene.

The effect of phenobarbital and 3-methylcholanthrene pretreatment on the biliary excretion of phenolsulphonphthalein (PSP) was investigated in male Wistar rats. The dye was injected at a single dose of 200 mumol/kg body wt. About 20% of the compound was excreted as a glucuronide in the controls, the liver UDP-glucuronyltransferase activity toward PSP being 0.064 +/- 0.005 nmol.min-1.mg protein-1. Treatment for two weeks with phenobarbital (354 mumol.kg body wt-1.day-1) caused a transient increase in conjugated and unconjugated PSP excretion, but glucuronyltransferase activity was not modified. 3-Methylcholanthrene pretreatment for 4 days (75 mumol.kg body wt-1.day-1) also enhanced biliary excretion of the dye, but the increase corresponded only to the glucuronide and glucuronyltransferase activity was significantly enhanced by 20%. Our data indicate that not only the rate of biotransformation but also other factors could be responsible for increased PSP biliary excretion following administration of microsomal enzyme inducers.