Testosterone Effect on Renin System in Rats

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Abstract
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 3 groups were sacrificed at 133, 78 and 75 days, respectively, at body weights ranging from 248-313 g. In the 2 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 3 groups but only in the older males was this increase statistically significant (P < 0.05). RS [renin substrate] was unchanged with treatment, 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. Testosterone may stimulate secretion of renin in at least the young male rat. Since testosterone stimulates levels of 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 mineralocorticoids could be playing a role, this is unlikely because aldosterone was unchanged.