Effects of corticosterone and dietary changes in the hen on ovarian function, plasma LH and steroids and the response to exogenous LH-RH

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Abstract
Ovarian regression was induced in hens by infusing 30 .mu.g corticosterone per/h, feeding diets deficient in Ca2+ or Na+ and by withdrawal of food and water. The weight of the ovary was most severely reduced by the corticosterone infusion. The total number of normal ovarian follicles weighing > 0.012 g was not altered by any of the treatments. The number of large yolk-filled follicles decreased while the numbers of smaller follicles and atretic follicles increased when ovarian regression was induced by dietary changes or hormone infusion as compared to normally fed or solvent-infused hens. These experimental treatments resulted in decreases in plasma concentrations of LH [luteinizing hormone] progesterone and estradiol, and increases in the plasma levels of corticosterone. These changes were immediate except for the low Na diet with which there was a delay of .apprx. 6 days. When fasted birds were fed oats and given water, plasma HL and estradiol, but not progesterone, increased. The infusion of corticosterone did not affect the ability of the pituitary gland to secrete LH after an injection of LHRH, but this response was reduced or eliminated by the other experimental treatments. The regression of the ovary induced by these experimental treatments evidently is a consequence of the reduction in the secretion of LH, which may itself be caused by increased plasma levels of corticosterone. Recruitment of follicles in the maturational stage which precedes entry into the hierarchy of large yolky follicles apparently was unaffected by all of the methods of inducing ovarian regression which were studied.