Effect of Hypophysectomy on Immobilization-Induced Elevation of Tyrosine Hydroxylase and Phenylethanolamine-N-methyl Transferase in the Rat Adrenal

Abstract

The depletion of adrenal epinephrine observed after immobilization stress in normal rats is even greater in hypophysectomized rats. The activities of adrenal tyrosine hydroxylase (TH) and phenylethanolamine-N-methyl transferase (PNMT), enzymes in the epinephrine biosynthetic pathway, are decreased following hypophysectomy. After repeated immobilization TH levels in hypophysectomized rats increase significantly but do not reach control levels. In hypophysectomized rats PNMT levels remain markedly decreased with repeated immobilization. When ACTH is administered to hypophysectomized rats before each period of immobilization there is less depletion of adrenal epinephrine and levels of TH and PNMT approach those found in sham-hypophysectomized immobilized rats. When dexamethasone is given prior to immobilization there is again less depletion of adrenal epinephrine and an increase in PNMT levels but no change in TH levels. Thyroxine does not increase epinephrine or enzyme levels in hypophysectomized immobilize...