DECREASED ANGIOTENSIN-II RESPONSE BUT UNALTERED CARDIOVASCULAR PRESSOR-RESPONSE TO INFUSED NOREPINEPHRINE AFTER SODIUM RESTRICTION AND CONVERTING ENZYME-INHIBITION

Although studies indicate that converting enzyme inhibitors such as ca ptopril influence beta-adrenergic physiology, the data on alpha-adrene rgic physiology is inconsistent. This study therefore examined the eff ects of captopril (50 mg/day for 5 days) during sodium restriction on the pressor response and on angiotensin II and neuropeptide Y levels t o infused norepinephrine (0.01 to 0.1 mug/kg/min) in 17 hypertensive a nd 27 normotensive subjects. Angiotensin II increased significantly in response to infused norepinephrine during placebo administration (p < 0.001) but not during captopril administration (p = 0.15). Neuropepti de Y levels decreased in response to captopril (p = 0.02). Despite the se changes the pressor response to infused norepinephrine was unchange d with captopril. These data support the conclusion that the antihyper tensive action of captopril is unrelated to alterations in norepinephr ine-mediated alpha-adrenergic pressor regulation. The finding of a dec rease in neuropeptide Y levels may have relevance to the therapeutic e ffects of captopril.