Effects of gonadal hormones on the zonal expression of rat hepatic phenol sulfotransferases.

Abstract

Estradiol benzoate (EB) and testosterone propionate (TP) were administered to male and female Wistar rats, and their effects on the zonal expression of hepatic phenol sulfotransferase (P-ST) activities were determined at pH 5.5 and 7.4. Cytosolic fractions from periportal (PP) and perivenous (PV) hepatocytes were prepared by the dual-digitonin-pulse perfusion technique. In control rats, P-ST activities assayed at pH 5.5 and 7.4 were higher in males than in females, and were higher in the PV fraction than in the PP fraction in both sexes. P-ST activities were increased by the administration of TP in the PP and PV fractions of females, whereas the same treatment diminished the enzyme activities in both fractions of the males. EB administration gave reduced P-ST activity at pH 5.5 of both fractions, irrespective of sex, but not a marked difference at pH 7.4. Chromatofocusing of PP and PV fractions revealed the presence of P-ST isoforms eluted at approx. pH 8.0 (peak 1), 7.5 (peak 2), 7.0 (peak 3) and 6.0 (peak 4). In male rats, peak 3, which showed high enzyme activity at pH 5.5 in the PP and PV fractions, was markedly decreased by EB treatment, whereas in females, peak 3 was present only in the PV fraction and was not affected by EB administration. TP treatment did not show remarkable changes in P-ST peaks in the males, while peaks 2 and 3 were increased in the females. Immunoblot analysis revealed the presence of multiple P-ST isoforms which showed different immunoreactivity and electrochemical properties.