Activity of catecholamine degrading enzymes in rat adrenal medulla and cortex after acute and repeated stress

The activity of catecholamine degrading enzymes (catechol-O-methyltransferase--COMT and monoamine oxidase--MAO) in separated adrenal cortex and medulla was measured in rats stressed by a singel or repeated immobilization. In controls, the activity of both enzymes was higher in adrenal cortex than in adrenal medulla. After stress, the activity of COMT in adrenal cortex was significantly decreased, while that in adrenal medulla was significantly increased. Moreover, the animals repeatedly immobilized showed lower COMT activity in both parts of adrenals when compared to first time stressed rats. The activity of MAO was not remarkably changed, but was increased only in adrenal medulla when expressed per mg protein, the decrease of which resulted from acute stress. It was concluded that the findings of changed activity of catecholamine degrading enzymes, namely a decreased activity of COMT in both adrenal cortex and medulla in repeatedly stressed rats, might show a possible participation of these enzymes in increased catecholamine content in adrenals of repeatedly stressed animals.