Dissociation of plasma atrial natriuretic peptide responses to upright posture and furosemide administration in patients with normal-, low renin essential hypertension and primary aldosteronism.

Plasma levels of atrial natriuretic peptide (ANP) were measured in patients with normal renin essential hypertension (n = 12), low renin essential hypertension (n = 11) and primary aldosteronism due to aldosterone producing adenoma (APA, n = 8) and idiopathic hyperaldosteronism (IHA, n = 3) after overnight rest in the supine position and after 4 h upright posture and furosemide administration. Plasma renin activity (PRA) and aldosterone (Aldo) levels were also determined. Compared to normal renin essential hypertension (33.6 +/- 2.2 pg/ml), basal plasma ANP was significantly higher in low renin essential hypertension (66.8 +/- 6 pg/ml), IHA (54.1 +/- 6.3 pg/ml) and APA before (62.4 +/- 4.9 pg/ml) but not after adrenal surgery (22 +/- 3 pg/ml). After upright posture and furosemide administration plasma ANP was decreased (p less than 0.01) in patients with low renin and, less markedly, with normal renin essential hypertension, however not in IHA and APA. In about half of the patients with low renin essential hypertension, unchanged PRA after upright posture and furosemide administration was associated with increased plasma Aldo and decreased ANP levels. We conclude that (i) the relatively high basal plasma ANP levels in low renin essential hypertension, IHA and APA may reflect the presence of volume expansion in these patients; (ii) the hormonal responses to upright posture and furosemide administration in patients with normal and low renin essential hypertension may indicate a counterregulatory role of ANP during activation of the renin-angiotensin-aldosterone system; (iii) the high plasma ANP, which is unresponsive to upright posture and furosemide administration, in patients with APA and IHA may be a potentially interesting new finding whose pathophysiological significance remains to be established.