[Opiate peptides of the adrenal medulla (author's transl)]

Significant concentrations of enkephalins are present in the adrenal medulla, notably in man, ox and dog. High molecular weight peptides precursors of enkephalin pentapeptide can also be demonstrated in the same tissue. Although the biosynthesis of enkephalins has not yet been completely elucidated, it seems to follow a pathway different from that of beta-endorphin. The secretion of enkephalins is regulated by the same mechanisms as the secretion of catecholamines. Enkephalins act locally by modulating catecholamine release, but since they are released into the systemic circulation, another, still ill-defined hormonal action is possible.