Corticotrophin Secretion by Ectopic Pituitary Glands

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Abstract
Five neonatal pituitary glands implanted under the kidney capsule of hypophysectomized rats had some maintenance effect on adrenal weight but the peripheral plasma corticosterone levels under normal environmental conditions were not significantly greater than those of hypophysectomized controls. One hour after ether inhalation, urethane injection, blood withdrawal or physical restraint there were significant elevations of peripheral plasma corticosterone reaching one third of the level in intact controls similarly treated. The response to blood loss in the graft-bearing rats was inhibited by dexamethasone at a dosage (1 [mu]g/ml in the overnight drinking water) which did not depress the response in intact controls. Infusion of lysine vasopressin released corticotrophin from the grafts but the effective dose (0.5 U in 30 min) was much greater than could be secreted endogenously. The results are ascribed to an accumulation of a physiological corticotrophin releasing factor in the peripheral circulation leading to a delayed release of corticotrophin from the grafts.