ACTH Secretion from the Pituitary Transplanted in Apposition with the Adrenal Cortex under the Renal Capsule

Abstract

In the pituitary homograft or autograft placed under the renal capsule of the rat, mature acidophils were hardly generated. However, in the pituitary implanted in apposition with the adrenal cortex in the adrenalectomized rat, the typical acidophils were differentiated to some extent (approximately 8.4%). The adrenocortical graft showed hyperactivity in terms of loss of fat droplets and elongation of cell-columns of the fasciculata. ¹⁴C-serine uptake by the host pituitary and the pituitary graft indicated that ACTH released from the graft itself acted directly upon the adrenal cortex, and that the secretion of ACTH from the pituitary graft might be regulated by a positive feedback mechanism. When the rat was exposed to a chronic stress of ether anesthesia, acidophils of the pituitary graft increased in number (approximately 15%) in proportion with the augmented ¹⁴C-serine uptake. The frequent occurrence of acidophils was postulated to be a specific phenomenon responsible for the pituitary-adrenal system, because no acidophils were differentiated in the pituitary implanted in apposition with the thyroid. By means of appositional transplantation, the possible secretion of ACTH from acidophils was clarified.