INHIBITION BY CORTISOL OF ACTH RELEASE FROM ANTERIOR PITUITARY TISSUE IN VITRO

The central basophilic region of bovine anterior pituitary glands was incubated for 30 minutes with varying concentrations of cortisol. Dialyzed incubation medium was subsequently assayed for ACTH activity by measuring the increased production of steroids from bovine adrenal cortex slices. Inhibition of ACTH release was evident with 5.5 × 10−11 M cortisol, but was more pronounced and consistent with 5.5 × 10−8 M or higher. Concentrations of 5.5 × 10−6 and 5.5 × 10−5 M were generally less effective in causing inhibition of ACTH release than were concentrations of 5.5 × 10−8 and 5.5 × 10−7 M.