LOSS OF ACTH ACTIVITY FOLLOWING INCUBATION OF PITUITARY TISSUE: INHIBITIONBY GLUCAGON AND BY PITRESSIN1

ACTH activity rapidly disappears from homogenates of anterior lobes of the rat pituitary incubated at 37° C in plasma or in water. Activity disappears relatively slowly from intact anterior lobes incubated in plasma at 37° C. The loss of ACTH activity is probably due to the action of a proteolytic enzyme or enzymes. Destructionis markedly slowed at 5° and at 100° C; the optimum pH for the destructive system is approximately pH 9. Addition of glucagon or Pitressin to the incubates inhibitsdestruction of ACTH. Plasma proteins and casein appear to have no or negligible protective effect. It has been pointed out that substances added to the medium of incubated pituitaries may increase the quantity of ACTH in the medium by inhibition of ACTH destruction as well as by stimulation of release from adenohypophyseal cells. ADRENOCORTICOTROPIC hormone (ACTH) activity disappears rapidly from neutral aqueous extracts of pituitary and from neutral aqueous solutions of crude preparations of ACTH whenthey are allowed to stand at room temperature (1).