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Microsomal glutathione S-transferase, UDP-glucuronyl transferase, and aniline hydroxylase activities were determined in liver, renal cortex, and small intestine of control, streptozotocin-diabetic, alloxan-diabetic, and untreated insulin-injected male Wistar rats. Renal microsomal glutathione S-transferase activity showed a direct linear relationship with insulin blood levels, in agreement with our previous report on cytosolic glutathione S-transferase. This result suggests a possible regulatory mechanism of insulin that needs to be further examined. The hepatic microsomal UDP-glucuronyl transferase was only decreased in streptozotocin-diabetic rats and was not restored by insulin treatment. Intestinal UDP-glucuronyl transferase exhibited an opposite response in streptozotocin-treated animals that was not normalized by the administration of insulin. Hepatic aniline hydroxylase showed the same behaviour as intestinal UDP-glucuronyl transferase. These results suggest that streptozotocin and (or) its metabolites have a direct effect on hepatic and intestinal UDP-glucuronyl transferase activity and on hepatic aniline hydroxylase activity. On the other hand, insulin regulation of enzyme activity varies from one organ to another.

Choleresis induced by dehydrocholate (DHC) stimulates the discharge into bile of lysosomes, which are implicated in the biliary excretion of proteins. Contrary to taurocholate-induced choleresis, DHC choleresis is not affected by microtubule (mt) inhibition. Therefore, the role of mt's in the biliary protein excretion during bile salt choleresis was analyzed in this study. Normal rats and rats treated with the mt poisons colchicine or vinblastine or with the acidotropic agent chloroquine (Cq) were used. The analysis of the protein component in bile was made on SDS-polyacrylamide gel, and the individual polypeptides were quantitated by densitometry. The excretion of bile polypeptides were compared with that of lysosomal acid phosphatase. Bile flow and bile salt output did not show changes on account of treatments. The biliary excretion of acid phosphatase was stimulated by DHC, and it was not affected by mt inhibitors but was markedly diminished by Cq. DHC choleresis produced different effects on the bile polypeptides. The biliary excretion of polypeptide of high molecular mass (84-140 kDa) was stimulated by DHC. Cq treatment increased their basal biliary excretions, whereas DHC-induced secretion was qualitatively and quantitatively similar to that of controls. The 69-kDa polypeptide (albumin) also increased during DHC-induced choleresis, but it showed a different excretory pattern. Cq treatment inhibited such an increase but no correlation with the excretory pattern of the lysosomal marker was found. The biliary excretion of polypeptides of low molecular mass (down to 14 kDa) suffered a transitory decrease and then a subsequent increase over basal values during the DHC choleresis.(ABSTRACT TRUNCATED AT 250 WORDS)

The activity of in vitro glutathione S-transferase towards 1-chloro-2,4-dinitrobenzene was examined in liver, renal cortex, and small intestine (duodenum, jejunum, ileum) after the in vivo treatment of male Wistar rats with streptozotocin or alloxan. The studies were performed at 2, 10, 24, and 48 h and 7 and 15 days after streptozotocin treatment or 24 and 48 h after alloxan treatment. The results indicated that while the blood levels of insulin-glucose did not show variations, there were no alterations of the glutathione S-transferase activity in the tissues tested. On the other hand, when the treatments caused modifications on blood insulin-glucose levels, there were changes of glutathione S-transferase activity in all tissues (except in the ileum) in such a way that a direct relationship between plasma insulin levels and glutathione S-transferase activity could be demonstrated. These results were also confirmed through insulin administration to control and diabetic rats. The data demonstrate a possible regulation of glutathione S-transferase activity by blood insulin and (or) glucose levels in the tissues tested.