Testosterone Effect on Renin System in Rats 1

Summary

Testosterone, 2.5 mg/day, was administered for 21 days to groups of female rats ovariectomized at age 105 days, male rats orchidectomized at age 50 days, and male rats orchidectomized as 26-day-old weanlings. The three groups were sacrificed at 133, 78, and 75 days, respectively, at body weights ranging from 248 to 313 g. In the two male groups there was a significantly greater plasma renin activity in testosterone-treated animals (P < 0.01) than in untreated controls. Plasma renin concentration rose with treatment in all three groups but only in the older males was this increase statistically significant (P < 0.05). RS was unchanged with treatment, however, except in the youngest group of males (P 0.05). This could have been due to conversion of testosterone to estrogens. Plasma aldosterone was not significantly altered by testosterone treatment. These results suggest that testosterone stimulates secretion of renin in at least the young male rat. Since testosterone has previously been shown to stimulate levels of the renin-like enzyme in mouse submaxillary gland, it is unclear from these experiments whether renal or submaxillary renin is involved. Although an indirect mechanism of antagonism by testosterone to action of mineralo-corticoids could be playing a role, this is unlikely because aldosterone was unchanged.

The testosterone and sterile vehicle used in this study were kindly supplied by Marvin R. Guthaus, Medical Services, the Upjohn Company, Kalamazoo, Michigan. Evelyn Fitzgerald rendered expert secretarial assistance.