[Direct effect of met-enkephalin on the synthesis and secretion of corticosterone by the adrenal glands of the rat].

ACTH (1 unit per 1 rat) induced a 6-fold increase of the corticosterone synthesis in adrenals and a 2-fold increase of its secretion into the blood. Met-enkephalin (15 micrograms/kg) also increase the corticosterone secretion, the level of the hormone in the blood, however, becoming even lower. Combined action of these two substances involved a greater increase of the hormone concentration in the gland than in case of each of them separately. The hormone content in the blood remained low in this case, too. In perfusion of an isolated adrenal gland with met-enkephalin (15 micrograms/ml), no increase in the corticosterone concentration was observed either in the perfusate samples. The data obtained suggest that met-enkephalin activates synthesis of corticosteroids, on the one hand, and inhibits their secretion into the blood, on the other hand, whereas ACTH activates both these processes.