ON THE SECRETION OF CORTICOTROPHIN BY THE HOMOTRANSPLANTED PITUITARY GLAND IN THE RAT

Abstract

Ten-week-old male rats bearing pituitary gland homotrans-plants beneath the kidney capsule (transplanted 3 weeks previously) were hypophysectomized 24 hours prior to testing the transplant''s ability to release corticotrophin (ACTH). Adrenal ascorbic acid depletion was used as the measure of ACTH release following the stimuli of ether anaesthesia and unilateral adrenalectomy, or these two stimuli, plus intravenous histamine. No significant adrenal ascorbic acid depletion occurred in such animals either 1 or 4 hours after these stimuli. The same results were obtained in rats that were hypophysectomized at the time of pituitary transplantation (7 weeks of age) and tested 3 weeks later. The transplanted pituitary glands contained ACTH at a concentration equivalent to that of the in situ glands. The rats bearing in situ as well as transplanted anterior pituitary glands until 24 hours prior to autopsy had adrenal weights slightly but significantly heavier than comparable non-transplant-bear ing animals. The results suggest that transplantation of the adenohypophysis beneath the kidney capsule interferes with an ACTH releasing process which is most likely mediated primarily through a direct connection with the CNS. The possibility that the slightly heavier adrenals in the transplant bearing animals might be due to a non-ACTH factor secreted by the transplant was also considered.