Hormone interrelationships affecting the selective uptake of 65Zn by the dorso-lateral prostate of the hypophysectomized rat.

Abstract

SUMMARY The efficiency of the dorso-lateral prostate (d.l.p.) of the rat to concentrate 65Zn was markedly depressed following hypophysectomy, but this glandular function could be maintained in the absence of the pituitary by the administration of suitable doses of chorionic gonadotrophin or testosterone. Removal of the testes in the hypophysectomized rat did not alter appreciably the maintenance effect of testosterone on the d.l.p. The effects of oestradiol on the efficiency of the d.l.p. to concentrate 65Zn were diverse and involved multiple sites of action. With a dose of 0·1 μg of oestradiol there was stimulation of uptake of 65Zn, and with 1 μg a sudden depression. The latter effect was paralleled by decreased size of the gland and histological evidence of marked cell atrophy. Neither the stimulatory nor depressant effects of oestradiol on 65Zn uptake could be reproduced in hypophysectomized rats maintained on gonadotrophin, indicating that these two actions of oestrogen involved the pituitary axis. Larger doses of oestradiol administered to hypophysectomized and hypophysectomized-castrated rats maintained on testosterone also exerted an inhibitory effect on the efficiency of the d.l.p. to concentrate 65Zn. There was maximal antagonism with an androgen: oestrogen ratio of 5:1, and as the proportion of oestrogen was increased there was a rebound rise in efficiency of the d.l.p. to take up 65Zn. The depression of 65Zn uptake by this peripheral-type of antagonism was not accompanied by depression in glandular weight. Even more striking was the observation that, in the face of this lowered glandular function, there was no evidence of any depression histologically or cytologically.