THE ACTIONS OF ANGIOTENSIN II ON CANINE MYOCARDIAL AND PLASMA CATECHOLAMINES

¹ Department of Pharmacology, West Virginia University Medical Center, Morgantown, West Virginia

A study was made of the stimulating effects of angiotensin on the sympathoadrenal system. Plasma and myocardial catecholamine levels were fluorometrically determined during and after 10min infusions of Hypertensin-CIBA, 0.1 µg/kg/min. Angiotensin caused a marked increase in plasma catecholamine levels and significantly increased norepinephrine (NE) levels in the right heart. After acute, bilateral adrenalectomy, angiotensin caused an initial increase in circulating NE levels but no change in myocardial NE levels. When angiotensin was infused after desipramine had been administered, there was a 50% decrease in myocardial NE levels and a potentiation of the elevation of plasma NE levels. The results indicated that myocardial uptake of circulating NE occurs; the increases in plasma NE levels in response to angiotensin are of both tissue and adrenal medullary origin. This study supports the reports that angiotensin increases the release of NE from adrenergic nerve endings.

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