Effects of sex steroid hormones on arginine vasopressin in intact and castrated male and female rats.

In the present study we have examined the effects of androgens and estrogens on circulating arginine vasopressin (AVP). Adult male Wistar rats had serum AVP levels of 0.4 microU/ml. Two weeks after bilateral castration, AVP rose to 2.6 microU/ml, but daily testosterone administration (100 microgram/100 g BW) to the castrate males prevented the AVP increase (0.8 microU/ml). During a normal estrous cycle, adult female Wistar rats had AVP values of 0.6 microU/ml during diestrus, 4.6 microU/ml on the morning of proestrus, 1.3 microU/ml on the afternoon or proestrus, and 1.5 microU/ml on the day of estrus. These changes in AVP paralleled the presumed changes in serum estradiol. Two weeks after bilateral ovariectomy of the adult female rats, AVP was 1.4 microU/ml but daily estradiol injections (100 microgram/100 g BW) to the castrate females produced a rise of serum AVP to 5.0 microU/ml. The results suggest an androgen inhibition and an estrogen stimulation of serum AVP levels.