Enzyme- and sex-specific differences in the intralobular localizations and distributions of aryl sulfotransferase IV (tyrosine-ester sulfotransferase) and alcohol (hydroxysteroid) sulfotransferase a in rat liver.

Aryl sulfotransferase (AST) IV and alcohol (hydroxysteroid) sulfotransferase a (STa) catalyze the formation of sulfuric acid esters from a diverse array of xenobiotic and endogenous molecules in the liver. Despite the fact that many studies have addressed the metabolic importance and catalytic characteristics of these two sulfotransferases, relatively little is known about their comparative in situ localizations and intralobular distributions in liver. The present investigation utilized specific rabbit antisera prepared against AST IV and STa for immunoperoxidase staining of serial sections from livers of male and female Sprague-Dawley rats and computer-assisted image analysis of immunohistochemical staining intensity by means of microdensitometry. The overall concentration of AST IV was greater in males than in females, although the intralobular distribution of the enzyme was similar in the livers of both male and female rats, wherein centrilobular hepatocytes contained a greater level of AST IV than did midzonal cells, and midzonal hepatocytes had a greater concentration of AST IV than did periportal hepatocytes. In marked contrast, STa was present in livers of female rats at a much greater overall concentration than in livers of male rats. Furthermore, whereas the intralobular distribution of the enzyme was similar in both males and females, STa was present at greater concentrations in periportal hepatocytes than in midzonal hepatocytes and at greater concentrations in midzonal cells than in centrilobular hepatocytes. Significant intrazonal heterogeneity in STa levels within hepatocytes was also observed, particularly in livers of female rats. These results indicate that, whereas the overall hepatic concentrations of these enzymes are clearly sex-dependent, the intralobular distributions of AST IV and STa are characteristic of each particular sulfotransferase.