Abstract

Changes in hemodynamic variables and plasma renin activity (PRA) induced by short-term alteration of blood pressure and sympathetic nervous system activity were studied in normotensive and hypertensive men on high-sodium and low-sodium intake. Blood pressure and heart rate alterations caused by standard cold pressor tests, amyl nitrite inhalation, phentolamine infusion, and phenylephrine infusion were recorded. PRA was measured at time 0, 5, 15, and 30 min. No change in PRA occurred in either group following cold pressore test and amyl nitrite inhalation. Phenylephrine suppressed PRA in normal but not hypertensive subjects, and phentolamine elevated PRA in normotensive and hypertensive subjects regardless of diet. Short-term stimulation of the sympathetic nervous system does not appear to elevate PRA in man. Suppression of PRA by an alpha agonist was not observed in hypertensives and may reflect barorecptor insensitivity in this group of subjects.