Interrelationship between Angiotensin and Catecholamines

Abstract

Urinary catecholamines were measured with an attempt for making differential diagnosis of various types of hypertension in which reninangiotensin system is or is not operating. This was based on recent evidences that angiotensin is a potent releaser of catecholamines and aldosterone from the adrenal glands. Twenty patients with essential hypertension, 5 malignant hypertension, 5 renovascular hypertension and 5 primary aldosteronism were subjected to the study. However, no changes in urinary catecholamine excretion were found and all values remained in normal range. Hypertensive doses of angiotensin infusion to normal men did not alter the output of adrenaline in urine, but did produce a marked decrease in noradrenaline excretion. In rats, intraperitoneal injection of angiotensin induced significant increase in noradrenaline content in the heart, while catecholamine levels in the adrenal glands were remained unchanged after angiotensin administration. Additional experiment showed that infusion of angiotensin to dogs enhanced the blood pressure response to tyramine. The data indicated that differential diagnosis of hypertension due to primary and secondary aldosteronism was impossible by means of urinary catecholamine assay. With the data obtained from angiotensin treatment in man and in animal, though it was indirect evidence, the authors concluded that there may be an inhibitory mechanism of the sympathetic nervous system in order to adapt to hypertensive state which is produced by angiotensin.