17α-oxidoreductase activity in kidneys of male and female mice of various ages

Abstract

Male and female mice at 0–120 days of age were used. Homogenates of kidneys were incubated with [ 14C]4-androstene-3,17-dione, and 17α-oxidoreductase activity per g tissue was examined. The activities of 17α-oxidoreductase in the kidneys of both sexes increased markedly with age during sexual development by up to 150-fold and reached the maximum values (2700 and 1500nmol/g/h in male and female kidneys, respectively) at 60 days of age. In the adult male mouse kidney, the activity in isolated cortex fractions was 14 times as high as the activity in isolated medulla fractions; in the medulla fractions renal tubules from the cortex accounted for 3–15% of the total tissue. Furthermore, histochemical examination showed the activity present only in the cortex, at which much higher levels in the tubules than in the glomerulus. Activity at 35–120 days of age was significantly higher in male kidneys than in female kidneys. The difference appears to be induced by testicular androgens during sexual development, since neonatal castration in males resulted in decreases of activity to levels similar to those in female kidneys. However, castration at 60 days of age showed no significant effect on the activity. The present results show that the activity per g tissue of 17α-oxidoreductase in the mouse kidney increases markedly with age, and that the activity is largely confined to the renal tubules of the cortex.