Effects of orchidectomy and sex steroids on vasopressin response to dehydration

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Abstract
The secretion of vasopressin has been shown recently to be influenced by gonadal steroids. To further evaluate the relevance of sex steroids in the control of vasopressin secretion, the vasopressin response to dehydration was studied in normal, castrated and sex-steroid treated castrated male rats. Short-term (3 wk) castration did not modify the vasopressin response to 48 h of water deprivation. Long-term (10 wk) castration, on the other hand, consistently reduced the vasopressin response by more than 50%. In both cases, the osmolality was unaffected. Treatment of long-term castrated rats with testosterone, dihydrotestosterone, or estradiol increased the vasopressin response to dehydration towards normal control levels. However, only estradiol could restore it to and beyond normal levels, although all 3 steroids were given in doses that were equipotent in bringing back to normal the plasma luteinizing hormone levels of the castrated animals. Angiotensin II generation may indirectly be augmented by estradiol treatment and this may account for the effect of estradiol here reported. No such mechanism, however, may be involved in the case of androgens; a direct modulatory effect at the hypothalamic level is postulated for explaining their influence on vasopressin secretion.

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