Effect of Orchiectomy on Pituitary Secretion of ACTH

Abstract

The effects of prepuberal gonadectomy on pituitary secretion of ACTH were studied in adult male rats. Plasma concentration of ACTH in unstressed adrenalectomized rats was increased following orchiectomy to 197% (95% confidence limits 134-289%) of the control level. Higher plasma ACTH concentrations were also observed in castrated animals with adrenals intact after the acute stress of ether anesthesia when compared to similarly stressed controls (159%; 121-215%). In both experiments, replacement with testosterone reversed the response to orchiectomy. Unstimulated release of ACTH in vitro by whole pituitary glands from orchiectomized donors, without or with testosterone replacement in vivo, did not differ from that of control glands. Addition of stalk-median eminence extract to the incubating glands, however, resulted in a greater R EMOVAL of the ovaries from rats results in decreased synthesis and release of ACTH (1). In addition, adrenal secretion of corticosterone is also significantly depressed, independent of changes in ACTH secretion (2). These effects are reversed with estradiol administration. The data thus demonstrate stimulation of the pituitary-adrenal system by estrogen at two different sites, i.e., significant and separable enhancement of secretion of both pituitary ACTH and adrenal corticosterone.

Androgen Inhibits the Increases in Hypothalamic Corticotropin-Releasing Hormone (CRH) and CRH-lmmunoreactivity following Gonadectomy

“…This in crease in CRH in the GDX male rat correlates with the increased CORT and ACTH response to physical and psychological stressors previously observed in the GDX male rat [15,16] and suggests that this pool of CRH is readily releasable. Although a previous study suggested that prepuberal gonadectomy of male rats did not affect the hypothalamic content of corticotropin-releasing bioactivity [20], our data are consistent with a more recent study showing increases in hypothalamic CRH peptide levels following long-term castration [21]. Also consistent with this study, we report here that more than 10 days are necessary to see an effect of castration on hypothalamic CRH content.…”

Sex differences in adrenocortical structure and function. XXVII. The effect of ether stress on ACTH and corticosterone in intact, gonadectomized, and testosterone- or estradiol-replaced rats

“…On the other hand, many lines of evidence indicate that the reactivity of pituitary corticotropes to CRF may play a decisive role in the appearance of sex differences in the response to ether stress. In fact, it has been demonstrated that in vivo CRFinduced ACTH release is depressed in ovariectomized as well as in testosterone-treated rats [5,6,24].…”

Specific regulation by steroid hormones of the amount of type I cyclic AMP-dependent protein kinase holoenzyme.

“…Indeed, the decline in type I isozyme activity in response to adrenalectomy and hypophysectomy, coupled with the failure of prostate and levator ani to respond to adrenalectomy, would support the concept of adrenal steroids contributing to the maintenance of kinase pools in the liver. A direct effect of androgens cannot be ruled out but work by other authors suggests that, although ACTH production in male rats increases after orchiectomy (25), castration has a direct effect on adrenocorticoid secretion by acting to increase 5a-reductase activity in the adrenal cortex, resulting in lowered levels of corticosterone and increased conversion to the 5a-reduced metabolites 5a-dihydrocorticosterone and 3#,,5a-tetrahydrocortisone (26). Therefore, the change in adrenal metabolism may be the important component in the decrease in kinase pools seen on castration.…”