Abstract

Opiate-like materials, as measured by the radioreceptor assay, were found in the adrenal gland of 7 mammalian species including man. The opiate-like materials are confined to the adrenal medulla, and followed a pattern identical to catecholamines on differential and isopycnic centrifugation. In the isolated perfused dog adrenal gland, acetylcholine stimulates a Ca²⁺-dependent secretion of opiate-like materials and catecholamines in the same molar ratio as they are stored within the chromaffin cell. Ba²⁺ also stimulates the secretion of both products from the adrenal gland. Separation of the opiate-like materials by Sephadex G-50 and reverse phase high pressure liquid chromatography indicates the presence of four peaks of opiate-like materials of molecular weights below 2,000. Two of these peaks comigrate in these systems with authentic met- and leu-enkephalins and react with the corresponding antibodies. These results indicate that enkephalins and other low molecular weight opiate-like materials are stored in and secreted from the chromaffin vesicles with catecholamines in the adrenal glands. These findings support a role for enkephalins as neurotransmitters and/or neurohormones. Also, they suggest that enkephalins and other opiate-like materials may exert important neuroendocrine functions outside the central nervous system.