POSSIBLE INVOLVEMENT OF ATRIAL-NATRIURETIC-FACTOR AND VASOPRESSIN IN ANTIHYPERTENSIVE MECHANISM OF CLONIDINE IN HUMANS

To appreciate the role of some neuropeptides in the antihypertensive m echanism of clonidine, 17 patients with essential hypertension were gi ven po clonidine 150 mug tid for 3 d. Plasma atrial natriuretic factor (ANF), vasopressin (Vas), and dynorphin A (Dyn A) were measured by ra dioimmunoassay. After the treatment, mean blood pressure (MBP), heart rate and 24 h urine norepinephrine, epinephrine were decreased, but no change was found in plasma Dyn A. The magnitudes of increased ANF and decreased Vas were correlated with the decreased MBP ( r = - 0. 57 an d 0. 53, respectively, P < 0. 05 ). These results suggest that both AN F and Vas are involved in the antihypertensive mechanism of clonidine.