Greater vasodilator responsiveness to atrial natriuretic peptide in low-renin essential hypertensives

Forearm vasodilator responses to atrial natriuretic peptide (ANP) were studied in twelve untreated patients with essential hypertension and twelve normotensive subjects. Alpha-human ANP (0.005 to 1.5 micrograms/min per 100 ml forearm volume) infused into the brachial artery increased forearm blood flow dose-dependently. This was paralleled by a decrease in forearm vascular resistance (FVR) which, at lower doses, was greater in essential hypertensives than in normotensives (P less than 0.001), and showed a lower ED50 for ANP in essential hypertensives (P less than 0.01). At higher doses of ANP the difference in vasodilator response between hypertension and normotension disappeared; the response to ANP was associated with a fall (P less than 0.01) in systemic blood pressure in hypertensives but not normotensives. At lower doses, the decreases in FVR were correlated directly with plasma renin activity in hypertensives (r = 0.656; P less than 0.05) but not normotensives. These data suggest greater vasodilator responsiveness to infusions of low doses of ANP in essential hypertensives, which is greater in low-renin states and blunted in high-renin states.