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H. L. Verjans and K. B. Eik-Nes

ABSTRACT

Testes of adult, male rats were exposed to a total dose of 1500 R of X-irradiation. Testicular weight decreased from day 8 after X-ray treatment. This decrease was, however, preceded by an increment of the testis weight on day 4 following treatment. X-ray treatment of testes was associated with significant increases in serum FSH. Testicular irradiation had, however, no effect on ventral prostate and seminal vesicles weights. Serum testosterone increased only on day 1, 2 and 4 after irradiation, while serum LH levels tended to increase from day 8 post-irradiation. These changes were not significant, however, when compared with non-irradiated controls. At 7, 13 and 20 days following 1500 R of bilateral, testicular X-irradiation, the hypothalamic-pituitary unit was still capable of responding to exogenous gonadotrophin releasing factor. Serum FSH may in male rats be regulated at least partly by circulating steroids of testicular origin and partly by an unknown factor of non-interstitial cell nature.

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H. L. Verjans and K. B. Eik-Nes

ABSTRACT

The effects of subcutaneous administration of steroids from the androstene, 5α-androstane, 5β-androstane, oestrene and oestratriene series on serum levels of LH and FSH and on ventral prostate weights were investigated in gonadectomized, adult male rats. Each steroid was administered for seven days in a standard dose of 100 μg per 100 g body weight per day. 5α-Androstanes disubstituted with oxygen in the positions 3 (3-keto or 3α-hydroxy) and 17 (17-keto or 17β-hydroxy) were effective in suppressing either one or both serum gonadotrophins. 5β-Androstanes and androstenes exhibited very little inhibitory effect in this respect. Potent suppression of serum gonadotrophins was observed following treatment with oestratrienes, the presence of only a phenolic A-ring in these oestrogens appeared sufficient for such suppression. 3 or 3β and 17 or 17β disubstituted (keto or hydroxyl) androstenes could entirely or partly prevent ventral prostate weight decrease post-gonadectomy. 5α-Androstane-3α,17β-diol, 5α-androstane-3α,11β,17β-triol and 5α-androstan-17β-ol-3-one were most potent, while 5β-androstanes and oestratrienes had no effect on this decrement. Regulatory processes by steroids at the hypothalamic-pituitary and at the ventral prostate level were not parallel.

The results indicate, however, that 3 or 3α and 17 disubstituted (keto or hydroxyl) 5α-reduced testosterone metabolites, of which 5α-androstan-17β-ol-3-one might be the principal one, are the main steroids directing androgenic regulation at both organ systems tested in the mature male rat.

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H. L. Verjans and K. B. Eik-Nes

ABSTRACT

Effect of intravenous administration of a synthetic gonadotrophin releasing factor (GnRF) on circulating LH and FSH concentrations was investigated in normal and gonadectomized, adult male rats injected subcutaneously each day during seven days with various doses of oestradiol-17β or 5α-dihydrotestosterone in sesame oil. Higher increase in serum LH and FSH levels subsequent to intravenously administered GnRF was observed in castrated control animals than in intact control animals, though this increment was not of significant nature for serum FSH. Pre-treatment of normal and gonadectomized rats with oestradiol-17β resulted in an augmented response of serum LH and FSH concentrations to GnRF iv. Pre-treatment of normal and gonadectomized rats with 5α-dihydrotestosterone diminished serum LH and FSH response following administration of the same amount of GnRF. For these steroids to affect the response pattern of serum LH and FSH to GnRF iv, higher doses were required in normal than in gonadectomized animals. The data indicate that oestrogen and androgen may act at different sites in the male hypothalamic-pituitary axis with respect to regulation of pituitary gonadotrophins.

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H. L. Verjans and K. B. Eik-Nes

ABSTRACT

Effect of intramuscular administration of ACTH or dexamethasone on blood serum levels of testosterone, LH and FSH was examined in intact and castrated, adult, male rats. Six IU ACTH or 1 mg dexamethasone were given daily for 7 days. Corticotrophin treatment had no influence on circulating testosterone, LH and FSH in intact or castrated male rats. Dexamethasone administration resulted in a slight elevation of serum FSH in intact animals but not in castrates. LH and testosterone remained normal in both intact and castrated animals injected with dexamethasone. Under our conditions of study the secretions from the adrenal gland appear to be insignificant for the regulation of pituitary secretion of gonadotrophins in the male rat.

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H. L. Verjans and K. B. Eik-Nes

ABSTRACT

The effect of subcutaneous administration of graded doses of C19 (androstene or androstane) steroids on serum levels of LH and FSH and on weights of accessory reproductive organs in gonadectomized, adult male rats were investigated. The C19 steroids were administered during 7 days in doses of 100, 50, 25, 12.5 or 6.25 μg per 100 g body weight per day. With the amounts of steroids used, 5α-dihydrotestosterone and 5α-androstane-3α,17β-diol had a high potency in preventing the rise of serum gonadotrophin concentrations and in curbing the decrease of weights of ventral prostates and seminal vesicles following orchidectomy. 5α-Androstane-3β,17β-diol showed no such effects. Positive feedback effects on serum gonadotrophins in castrates were observed following injection of certain doses of some steroids. Effects of steroids on accessory reproductive organs did not always correlate with those on gonadotrophic function of the hypothalamic-pituitary unit.

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H. L. Verjans and K. B. Eik-Nes

ABSTRACT

Effects of subcutaneous administration of various doses of different steroids on serum levels of LH and FSH in normal, adult male rats were investigated. Each steroid was injected daily during 7 days in doses of 50, 25, 12.5 or 6.25 μg per 100 g body weight. Ring A 5α-reduced testosterone metabolites exerted high activity in suppressing serum LH and FSH levels. 5α-Androstane-3β,17β-diol had in the doses tested, however, no such effects on serum gonadotrophins. Serum LH concentrations in normal rats appeared more sensitive to steroid treatment than serum FSH concentrations.

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H. L. Verjans, H. J. van der Molen, and K. B. Eik-Nes

ABSTRACT

Serum levels of LH, FSH and testosterone were measured by radioimmunoassay in intact and castrated, adult, male rats after testosterone was administered subcutaneously for seven days in doses ranging from 25 to 200 μg per 100 g body weight per day. Such treatment increased circulating testosterone both in intact and castrated rats, but its effects on serum gonadotrophins were different in these animal groups. All doses of testosterone suppressed serum LH and FSH in the normal rat. In the castrates, treatment with the lowest dose of testosterone resulted in serum LH levels significantly above the high castrate levels, while serum FSH tended to drop. Administration of the highest doses of testosterone did not depress serum LH and FSH in the castrates to those of intact, normal animals, though serum testosterone in these castrates was much higher than in normal, male rats. It is concluded, that the sensitivity of the hypothalamic-pituitary system for daily, subcutaneous testosterone administration during seven days is not the same in the intact and castrated, adult, male rat and that testicular factors different from testosterone may play a role in regulating production and/or secretion of gonadotrophins by the hypophysis in male animals.

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H. L. Verjans, F. H. de Jong, B. A. Cooke, H. J. van der Molen, and K. B. Eik-Nes

ABSTRACT

The effects of subcutaneous administration of oestradiol benzoate (EB) on the weights of sex organs and on levels of testosterone and gonadotrophins in normal adult male rats have been studied. Doses of EB varied from 0.01 to 100 μg and were administered daily for seven days. Administration of 100 μg EB resulted in suppression of pituitary LH, while serum LH levels were already decreased after treatment with EB ≧ 1 μg. Pituitary and serum FSH levels were suppressed after administration of 100 and 10 μg EB respectively. Testicular tissue and serum levels of testosterone decreased after treatment with amounts of EB ≧ 1 μg. These decreased androgen levels were also reflected in a concomitant decrease in the weights of the ventral prostate and seminal vesicles. A decrease in the weight of the testes was obtained following a dose of EB ≧ 10 μg.

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H. L. Verjans, K. B. Eik-Nes, J. H. Aafjes, F. J. M. Vels, and H. J. van der Molen

ABSTRACT

The influence of treatment with various doses of testosterone propionate, 5α-dihydrotestosterone propionate or oestradiol benzoate on serum levels of LH and FSH (measured by radioimmunoassay) and on weights of ventral prostates and seminal vesicles was investigated in castrated, adult, male rats. For depression of the high, castrate levels of serum gonadotrophins with either of these steroid esters, the inhibition curves were different for LH and for FSH. Serum LH was kept at levels encountered in intact, adult, male rats by lower doses of steroid ester than was serum FSH. Oestradiol benzoate was the most potent suppressor of the serum gonadotrophins among the steroid esters tested, testosterone propionate the least. Treatment with low doses of oestradiol benzoate, however, resulted in serum FSH levels significantly above those of castrates treated with vehicle only. Finally, administration of a synthetic LH-releasing factor to testosterone propionate, 5α-dihydrotestosterone propionate or oestradiol benzoate treated, castrated, adult, male rats resulted in a further release of both LH and FSH. The latter effect was more pronounced in oestradiol benzoate treated castrates than in testosterone propionate or 5α-dihydrotestosterone propionate treated castrates.