Synthetic peptide immunocortin stimulates the production of 11-oxycorticosteroides by rat adrenal cortex through ACTH receptors

[Stress-protective effect of the synthetic ACTH-like peptide leucocorticotropin]

We found that the tritium-labeled synthetic ACTH-like octapeptide leucocorticotropin corresponding to the 81-88 sequence of the precursor of human interleukin-1alpha ([3H]GKVLKKRR) is bound by the ACTH receptor of rat adrenal cortex with a high affinity and specificity (Kd 2.2 +/- 0.1 nM). This peptide was shown to exert no effect on the adenylate cyclase activity of the membranes of rat adrenal cortex in the concentration range from 1 to 1000 nM. Leucocorticotropin administration three times at doses of 10-20 microg/animal did not change the level of hydroxycorticosteroids (11-HOCS) in the rat adrenal glands in the absence of temperature action. At the same time, the peptide abolishes (at a dose of 20 microg/animal, three times) or significantly decreases (at a dose of 10 microg/animal, three times) the dramatic increase in the 11-HOCS content in the adrenal glands occurring in the case of cold or heat shock. Thus, leucocorticotropin normalizes the 11-HOCS level in the rat adrenal cortex during stress. The stress-protective effect of the peptide is mediated through the ACTH receptor.