Javier Argos González

Influence of acute ethanol administration on hepatic glutathione metabolism in the rat.

The effect of acute ethanol administration on the hepatic metabolism of glutathione was studied in male Wistar rats. Animals fasted for 18 hr received ethanol (5 g/kg body wt.) through a gastric tube as a 20% (w/v) solution in 0.154 NaCl. Four hours after administration of ethanol liver glutathione content was decreased by 21% when compared to saline-treated controls. A significant reduction (28%) was also found in gamma-glutamylcysteine synthetase activity and plasma glutathione levels were increased non significantly by 17% with respect to control rats. Glutathione S-transferase activity in the liver of ethanol-treated animals was decreased by 28% but no change was found in total glutathione peroxidase activity. The results indicate that the lowered glutathione synthesis could be an important factor contributing to the reduction of hepatic glutathione concentration following the acute ingestion of ethanol.

Effect of chronic ethanol feeding on glutathione and glutathione-related enzyme activities in rat liver

The effects of chronic ethanol consumption on liver glutathione concentrations and glutathione-related enzyme activities were studied in rats over a period of 1-9 weeks. The animals received a liquid diet containing 36% of calories as ethanol or isocaloric carbohydrate. Glutathione concentrations were significantly enhanced following ethanol intake with increases of 99% after 3 weeks and a progressive decrease thereafter. Glutathione S-transferase activity reached a maximum increase of 36% after 2 weeks of ethanol feeding. Glutathione peroxidase activity remained unchanged for the first 6 weeks of treatment, with a tendency to decrease in the last weeks of ethanol consumption. Our findings indicate that chronic ethanol administration profoundly modifies the hepatic metabolism of glutathione and may thus have important effects on the detoxification of xenobiotics by the liver.

Bile pigment formation and excretion in the rabbit

Bile and plasma levels of biliverdin and bilirubin, together with the hepatic biliverdin reductase and bilirubin UDP-glucuronosyl transferase activities, were studied in the rabbit. No biliverdin could be detected in the blood plasma. The bilirubin concentration in blood was 7.81 +/- 0.79 mumol/l. Biliverdin was the predominant pigment in bile (63%). Hepatic biliverdin reductase activity was 0.086 +/- 0.016 nmol/mg protein/hr. The synthesis of bilirubin was apparently limited by the enzyme activity. Most of the bilirubin in bile was conjugated (90%) with monoconjugates predominating (75%). Hepatic UDP-glucuronosyl transferase activity was 2.65 +/- 0.18 and 1.14 +/- 0.16 mumol/mg protein/hr with and without activation, respectively.

Changes in biliary secretion and lactate metabolism induced by diethyl maleate in rabbits.

Diethyl maleate is a compound which binds with glutathione by means of a glutathione S-transferase and is excreted into bile leading to a rapid depletion of hepatic glutathione. In the rabbit, the activity of the enzyme is fairly low and we were thus prompted to study the possible effects of diethyl maleate on biliary secretion and metabolic status in this species. The administration of diethyl maleate induced a transient choleresis followed by cholestasis. The choleresis coursed with increases in the biliary output of sodium and unaccounted anions, whereas those of chloride, bicarbonate and bile acids were unaffected. Our data seem to confirm that choleresis is due to the osmotic activity of diethyl maleate compounds excreted into bile, as has been reported in rats and dogs. The cholestasis observed coursed with falls in the outputs of sodium, chloride and bicarbonate though that of bile acids remained constant. Following diethyl maleate administration, a metabolic acidosis appeared with progressive increases of blood lactate concentration. In bile the concentration of this anion closely followed that of plasma. The cholestasis is attributed to a lowered biliary secretion of bicarbonate probably secondary to the metabolic alteration. The hepatic values of cytoplasmatic and mitochondrial NADH/NAD ratios and of adenine nucleotide concentrations suggest that the increase in blood lactate results rather from a fall in its hepatic utilization that from an increase in its production.

Role of glucose reabsorption from bile on hyperglycaemia-induced cholestasis in the rabbit

The effect of glucose administration on bile secretion of glucose and bile flow and composition was studied in the rabbit. After intravenous glucose infusion at 83 mumol/kg/min a mean bile concentration of 12.7 +/- 1.8 mg/dl was reached. Intraportal administration of phlorizin enhanced bile glucose concentration to 169.6 +/- 18.1 mg/dl, suggesting the presence of a system for transferring glucose from bile to liver in the biliary tree of the rabbit. A significant correlation between bile flow and plasma glucose levels could be demonstrated. A cholestatic effect appeared in glucose-infused rabbits with a decrease in bile flow by about 40% during the second hour of infusion. Both bile acid and inorganic electrolyte output were significantly lowered. Cholestasis was maintained after phlorizin administration. Possible explanations for this effect are discussed.

Heterogeneity of rabbit hepatocytes for bile secretion after acinar zone 3 damage induced by bromobenzene: Effect of bilirubin and bile salt infusions

Anaesthetized rabbits were used to study the effect of bromobenzene-induced hepatic damage to the acinar zone 3 on bile flow, bile salt, sodium secretion as well as bilirubin transport in basal conditions or with infusion of sodium glycodeoxycholate. The bromobenzene-pretreated animals exhibited in basal conditions a lower bile flow (44%) than that of the controls, with a smaller decrease in bile salt output (27%) and sodium output (29%), whereas no modification in endogenous bilirubin excretion was observed. The bile salt independent fraction of secretion (BSIF) was reduced significantly after the toxic lesion both in terms of absolute and relative values. The hepatocytes of the periportal zone were capable of excreting the totality of bilirubin presented to the liver, regardless of the extent of bile flow or the input of bile salts. The infusion of bilirubin at 1.0 mumole/kg/min led to a fall in bile flow which was attributed to the interference of the pigment with the BSIF. The maximal bilirubin excretion was significantly smaller in bromobenzene-pretreated animals than in the controls, which could be due to the incapacity of the intoxicated rabbits to recruit quiescent hepatocytes. When glycodeoxycholate was administered under conditions of maximal bilirubin transport, bile flow increased as did bile salt secretion in both controls and animals with damaged livers. However, clear differences persisted between the two, which could be attributed not only to the volume fraction of necrosis but also to an interference by bilirubin with the hepatic handling of bile salts. Maximal bilirubin excretion increased in a similar way in both groups after glycodeoxycholate administration. It is proposed that glycodeoxycholate infusion facilitates the hepatic depletion of bilirubin, probably by stimulating transport processes.

Effect of pentobarbital or urethane on bile secretion and chemical composition of blood in the rabbit

A study was made of the effects of anaesthesia with pentobarbital and urethane on the bile secretion and the chemical composition of the blood of New Zealand rabbits. Neither of the agents was observed to affect arterial pH or pO2, but with urethane pCO2 values decreased significantly. This was associated with a pronounced hyperglycaemia. Bile flow was significantly higher in pentobarbital-anaesthetized animals than in urethane-anaesthetized animals, a phenomenon that can be attributed to a different canalicular flow and that will not be related to differences in the bile-acid-dependent fraction of secretion. Under both anaesthetics, bile sodium concentrations were greater than those found in plasma, which can be explained by the formation of micelles with low osmotic activity. Bile bicarbonate concentrations proved to be greater than those observed in plasma. Plasma calcium concentrations were significantly lower with urethane than with pentobarbital, whereas in bile the situation was reversed; both these aspects are discussed.

Evolution of Biliary Secretion during Bile Diversion in Normal and Two-Thirds Hepatectomized Rats

The effect of the interruption of the enterohepatic circulation on bile production in anesthetized rats both before and after two thirds partial hepatectomy (PH) was studied. Both in the control animals and in the different periods after PH, interruption of the enterohepatic circulation led to significant decreases in bile flow and bile acid and sodium output. The evolution of choleresis in all the experimental groups was seen to follow a parallel course to that of sodium output and showed qualitative and quantitative discrepancies with the behavior of bile acid output. The cumulative secretion of bile acids expressed per 100 g of body weight was comparable in the controls and at 384 h after PH, though only in the former did the bile acid circulating pool size seem to be depleted. This depletion was more delayed than that described for conscious nonfasting rats. At 96 and 384 h after PH both cumulative bile flow and cumulative sodium secretion expressed per gram of liver were greater than those of the control animals. The choleretic capacity of the bile acids and the bile acid independent fraction of bile flow were significantly modified in the different posthepatectomy periods.

Influence of Dehydrocholate on Bilirubin Transport into Bile in the Rat

The effect of an intravenous infusion of sodium dehydrocholate on the maximum biliary transport (Tm) of bilirubin was studied in Wistar rats anesthetized with sodium pentobarbitone. Infusion of the synthetic bile salt at 0.24 mumol/min/100 g gave rise to a marked increase in bile flow (69%). The biliary output of taurocholate, phospholipid or cholesterol, compounds which from mixed micelles in bile, was not modified. Neither did the Tm of bilirubin undergo any significant changes, with drops in the bile concentration of the pigment. Our experimental results revealed that bile flow induced by dehydrocholate is not a determining factor of the Tm of bilirubin in the rat.

Effects of two-thirds hepatectomy on sulfobromophthalein handling by the rat liver

The modifications in the hepatic transport of sulfobromophthalein (BSP) were studied after partial hepatectomy (p.h.) in Wistar rats. The biliary excretion of BSP, injected i.v. at 150 mumol/kg, decreased in the early periods after p.h., with a disappearance of the choleretic effect induced by the dye in sham-operated animals. The impairment in the biliary BSP excretion corresponded to the conjugated fraction and was accompanied by a lowered glutathione S-transferase activity in the liver.