Supraphysiological testosterone administration alters renal 25‐hydroxyvitamin D‐3 1α‐hydroxylase protein expression in female rodents

Abstract

The enzyme 25‐hydroxyvitamin D 1α‐hydroxylase (CYP27B1) converts circulating 25‐hydroxyvitamin D to its active form, 1,25‐dihydroxyvitamin D. The effects of testosterone (T) on CYP27B1 expression within the kidney, an androgen sensitive organ, remain unclear. The purpose of this study was to determine whether gonadectomy (GNX) or T alter renal CYP27B1 protein expression. 3 month old male and female F344 rats (n = 5/group) received SHAM surgery + vehicle (V), GNX + V, or GNX + supraphysiological T‐enanthate (GNX+TE) for 28 days. The kidney was removed at sacrifice and CYP27B1 expression was measured in the renal cortex by Western blot. GNX+TE increased kidney mass by 19% and 28% in males and females compared with Shams and by 29% and 26% compared with GNX + V (p < 0.05). No differences in renal CYP27B1 expression were present between intact males and females. GNX did not alter CYP27B1 protein expression in either sex. No change in CYP27B1 protein expression was observed in GNX+TE males. However, renal cortex CYP27B1 protein expression was reduced by 28% in GNX+TE females compared with SHAMs (p < 0.05). Our results indicate that supraphysiological TE down‐regulates renal cortex CYP27B1 protein expression in female rodents, through a yet to be identified mechanism. Future studies examining the effects of T on the activity and expression of CYP27B1 should account for androgen induced alterations in kidney mass.