ARGININE AND ORNITHINE METABOLIZING ENZYMES IN TESTOSTERONE-INDUCED HYPERTROPHIC MOUSE KIDNEY

Administration of testosterone to female mice causes hypertrophy of their kidneys with spectacular induction of ornithine decarboxylase and significant increase in the level of putrescine. We tried to find out whether testosterone treatment affects also the renal activities of enzymes participating in the formation and utilization of ornithine, specifically arginase and ornithine aminotransferase, and whether they are dependent on putrescine level. Swiss, CFW, DBA2 or F1 (CFW x DBA2) female and male mice were injected with testosterone (125 mg/kg) or CB 3717 (100 mg/kg). DFMO was applied in the drinking water. The activities of the enzymes were determined 24 hr or 5 days after administration of CB 3717 or testosterone, respectively. Renal activities of ornithine decarboxylase (ODC), arginase and ornithine aminotransferase (OAT) were found to be sex-differentiated. The highest activity of ODC was characteristic for the kidneys of males, whereas those of arginase and OAT for the kidneys of females. In the kidneys of testosterone-treated female mice a decrease (50%) of OAT, and a significant increase of arginase activities (up to 200%), were observed. In the males these changes were less pronounced. DFMO, which completely inhibited the activity of renal ODC, did not influence significantly the testosterone-induced arginase and the testosterone-decreased OAT. Arginase and OAT, in contrast to ODC, were not changed in CB 3717-induced hyperplastic kidney. The study showed testosterone-induced differential changes in the activity of two enzymes involved in ornithine biosynthesis and catabolism which accompanied ODC induction in female mouse kidney. However ODC induction was not a prerequisite for these enzymatic changes as they did not follow ODC activation by CB 3717, and were not affected by DFMO, a specific inhibitor of ODC.