Compensatory increase in adrenomedullary angiotensin-converting enzyme activity (kininase II) after unilateral adrenalectomy

Angiotensin-converting enzyme (ACE, kininase II, dipeptidyl carboxypeptidase, EC 3.4.15.1) was characterized in the adrenal medulla of male Sprague-Dawley rats. Rat adrenal medulla and lung ACE were similar in their susceptibility to Cl- activation and to the inhibition by EDTA, captopril, bacitracin and thiorphan, suggesting that rat adrenal medulla and lung ACE have similar properties. Changes in right adrenal weight and in adrenomedullary ACE activity 5 and 12 days following left unilateral adrenalectomy (UADX) were examined. Compensatory adrenocortical hypertrophy 12 days following UADX was associated with a significant increase in adrenal medullary ACE activity. This change was due not to a modified affinity of ACE for the substrate but to an alteration in ACE maximal velocity or number of available molecules. UADX had no effect on adrenocortical ACE activity. When UADX was combined with right splanchnic denervation, the increase in adrenomedullary ACE activity was blocked. The results support the existence of a functional ACE in adrenal medulla that is under neuronal control.