Significance of intermedin activity in adrenocorticotropic hormone preparation

ACTH receptors in the adrenal: specific binding of ACTH-125I and its relation to adenyl cyclase

Pure monoiodo ACTH-(125)I was prepared that was biologically active and free of unlabeled ACTH. Extracts of adrenal cortex that contained ACTH-sensitive adenyl cyclase, bound ACTH-(125)I; extracts that lacked the ACTH-sensitive cyclase did not bind ACTH-(125)I. Unlabeled ACTH inhibited the binding of ACTH-(125)I. Five ACTH derivatives which varied widely in biological activity were tested. All inhibited the binding of ACTH-(125)I in direct proportion to their biological activity. Albumin, insulin, and four unrelated iodinated hormones were inert. The addition of excess hormone or acetic acid produced rapid dissociation of bound ACTH-(125)I. This study demonstrates directly the binding of ACTH to its biologically significant site.

Corticotropins (ACTH). X. Biological investigations on alpha-corticotropin

Purified alpha-corticotropin has been reported to exercise the following biological effects: (a) stimulation of the adrenal glands in normal and hypophysectomized rats, (b) production of blood eosinopenia in hypophysectomized rats, (c) maintenance of muscle glycogen in hypophysectomized rats, (d) inhibition of growth-promoting activity of somatotropin, (e) stimulation of melanocytes in the skin of frogs, (f) mobilization of fat into the liver of fasted mice, (g) stimulation of the accessory sex glands of castrated-hypophysectomized male rats, (h) induction of deciduoma formation in hypophysectomized-oophorectomized rats, and (i) elevation of the total red cell volume in hypophysectomized rats. alpha-Corticotropin has also been shown for the first time to act in synergism with lactogenic hormone as an essential galactopoietic hormone. The ability of alpha-corticotropin to elicit biological responses in the absence of the adrenal cortex is discussed.