Effects of adrenalectomy and adrenal steroids on norepinephrine synthesis and monamine oxidase activity

Rat heart norepinephrine (NE) tunover was increased 6--10 days after bilateral adrenalectomy. This increase was prevented by administration of deoxycorticosterone acetate (DOCA) but not by either hydrocortisone or corticosterone. Blood pressure decreased following adrenalectomy. This decrease was prevented by DOCA, hydrocortisone and corticosterone. Monoamine oxidase (MAO) activity increased in the heart but not in the liver following adrenalectomy. DOCA prevented the increase in heart MAO activity whereas hydrocortisone and corticosterone were ineffective. In intact animals, heart and liver MAO activity were not changed by 5 days of cold exposure, a procedure which increases NE turnover. It is suggested that the increase in heart NE turnover may be related to the increase in MAO activity seen after adrenalectomy.