Release of some cytosolic (aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase) and brush border (gamma-glutamyltransferase and alkaline phosphatase) enzymes from renal cortical slices was studied in vitro. Renal cortical slices were prepared freehand from 3-month-old male and female Wistar rats of different hormonal status. Some male and female rats were castrated at 1 month of age and a portion of castrated males and of naive males and females were s.c. treated with testosterone (10 mg kg-1 body wt.) on alternate days for 3 weeks. Females had higher alanine aminotransferase (77.5 +/- 2.8 nmol 100 mg-1 tissue), lactate dehydrogenase (5.01 +/- 0.24 mumol) and alkaline phosphatase (1.63 +/- 0.15 mol) activities than male rats (20.4 +/- 0.9, 3.99 +/- 0.19 and 0.91 +/- 0.02, respectively). On the contrary, aspartate aminotransferase and gamma-glutamyltransferase were similar. Among cytosolic enzymes, alanine aminotransferase and lactate dehydrogenase appeared to be sexual hormone-dependent enzymes: castration significantly increased enzyme activities in males (49.6 +/- 1.1 for the former; 5.30 +/- 0.15 for the latter) and caused significant decreases in females (alanine aminotransferase only 47.1 +/- 1.5), whereas testosterone pretreatment decreased activities in cortical slices from female (48.1 +/- 3.6 and 3.81 +/- 0.07, respectively) and castrated male (27.4 +/- 1.8 and 4.05 +/- 0.15, respectively). Moreover, exogenous testosterone increased aspartate aminotransferase in males (1.05 +/- 0.01 mumol) and castration increased it in both sexes. The activity of brush border enzymes was increased by testosterone pretreatment and decreased by castration (mainly alkaline phosphatase).