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Different numbers of rat pituitary glands, taken from male and female rats before and after puberty, were transplanted into various sites in female rats at different stages of the oestrous cycle. Ovulation was checked by counting ova in oviducts on the next expected day of ovulation. Ovulation was induced by transplantation beneath the kidney capsule in early dioestrus of half, one or three glands from 35- to 41-day-old male rats (18·6 ± 3·1 (s.e.m.), 32·6 ± 2·8 and 49·8±4·8 ova shed respectively). The transplantation of glands from mature female rats did not induce superovulation but inhibited the expected ovulation. The most effective stage for inducing superovulation was early dioestrus and, to a lesser extent, oestrus; transplantation during late dioestrus was ineffective. The effective sites of transplantation were beneath the kidney capsule and intramuscularly but not subcutaneously. Representative pituitary glands from 35- to 41-day-old male rats and adult female rats were assayed for LH and FSH content to interpret the mechanisms of superovulation. The pituitary glands from the male rats contained larger amounts of LH and especially of FSH than those found in the female rats. The experiments indicated that superovulation can be induced successfully by the transplantation of a single pituitary gland from male and immature female rats without any additional treatment with human chorionic gonadotrophin; the failure of the female pituitary transplants to induce superovulation may be due to the insufficient content of LH and FSH.
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ABSTRACT
The effect of human recombinant activin-A on adrenal steroidogenesis was studied in cultured bovine adrenocortical cells. Activin-A significantly reduced cortisol output from ACTH (10nmol/l)-stimulated adrenocortical cells incubated for 24 hours in a dose-dependent manner (10, 100 and 500ng activin-A /ml suppressed cortisol secretion by 19, 33 and 40%), although no significant effect was observed in the case of 3 h incubation. Dehydroepiandrosterone (DHEA) secretion from ACTH-stimulated adrenocortical cells incubated for 24 h was also decreased by the addition of activin-A in a dose-dependent manner. (10, 100 and 500ng activin-A /ml suppressed DHEA secretion by 22, 56 and 58%).
These inhibitory effects of activin-A (100ng/ml) on cortisol and DHEA secretion were partially blocked by the addition of follistatin / FSH-Suppressing Protein (200ng/ml). In contrast, activin-A treatment resulted in no significant decrease in aldosterone secretion. There were no significant effects of activin-A on basal secretions of cortisol, DHEA or aldosterone from adrenocortical cells. These results suggest that activin-A has a direct inhibitory effect on ACTH-stimulated bovine adrenocortical steroidogenesis.
