THE EFFECTS OF OESTRADIOL ON CORTISOL SECRETION BY THE ISOLATED DOG ADRENAL

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Abstract
Perfusion of 17[beta]-estradiol into the arterial circuit of isolated dog adrenal preparation, secreting cortisol at a maximal rate, produced a dose related inhibition of cortisol secretion, significant at the 20 [mu]g and 100 [mu]g dose levels. Perfusion of 100 [mu]g of 17-estradiol resulted in a similar inhibition of cortisol production of comparable magnitude. In isolated adrenals prepared in hypophysectomized dogs, secreting cortisol at resting rates, no difference in secretion rates was apparent in animals which had been previously oophorectomized in comparison with those animals with intact ovaries. Following 17[beta]-estradiol perfusion, the cortisol secretion rates in the oophorectomized animals fell. No sex differences in the dog were detected in cortisol secretion rates either at resting or at maximal secretory levels. These studies demonstrate an inhibitory action directly on the dog adrenal cortex of both the 17[beta] and 17[alpha] isomers of estradiol. There was no evidence obtained for an estradiol stimulatory effect. Estrogens may exert a variety of effects on the hypothalamic-pituitary-adrenal system. The anatomic site of action as well as the physiological significance of some of these effects are uncertain. Despite numerous studies in several species on the action of estrogens on this system, many questions remain to be resolved.