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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.
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Search for other papers by THELMA C. GOULD in
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SUMMARY
The data presented in this paper illustrate a distinct yearly cycle of activity in the capacity of the dorso-lateral prostate (d.l.p.) of the male laboratory rat to concentrate injected 65Zn. From 60 to 85% more 65Zn was taken up per mg of glandular tissue in the months of February-March and June-July than at other times of year. Studies of the corresponding weights of the d.l.p. showed trends towards lower glandular weights in January and in April; the maximum difference noted between high and low glandular weights was, however, only 28%. That this increased uptake of 65Zn by the d.l.p. in February-March and June-July was a strong inherent feature was illustrated by the fact that rats of various ages, from 8 weeks to 1½ years, showed this increased glandular activity at these times of year. Of all the animals tested only the immature rat of 5 weeks of age and the exhausted breeder did not manifest this seasonal activity.
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SUMMARY
Eleven days following hypophysectomy the capacity of the rat testis to take up administered 65Zn is markedly depressed below values noted in intact controls, even though microscopically there is only a slight diminution in the number of germinal epithelial and interstitial elements. Interstitial cell-stimulating hormone (ICSH) in doses of 5 μg./day administered from the 5th to the 10th day after operation completely prevented the fall in total 65Zn uptake of the testis following removal of the pituitary. Follicle stimulating hormone (FSH) was less effective than ICSH in this regard. The possibility of the FSH effect being due to contamination with ICSH is considered. Growth hormone and prolactin in doses of 200 μg./day administered from the 5th to 10th day after operation were ineffective in preventing the fall in 65Zn uptake of the testis following hypophysectomy.
