[Correlations between blood pressure, blood volume, plasma renin and urinary catecholamines in normal subjects and in patients with benign essential hypertension].

Interrelations between blood pressure, circulatory volume, plasma renin activity (PRA) and urinary catecholamine excretion rates were studied in normal subjects and patients with benign essential hypertension. Mean plasma or blood volumes related to lean body mass, products of blood volume and the logarithm of PRA, and catecholamine excretion rates did not differ significantly as between normal and hypertensive subjects. In both normal subjects and hypertensive patients, blood pressure correlated positively with noradrenaline excretion rate (r = 0.40 and 0.36 respectively; p less than 0.025), but not with adrenaline excretion, circulatory volume or the volume-renin product. The logarithm of PRA correlated inversely with mean blood pressure in normal subjects (r = -0.40; p less than 0.001), but not in hypertensive patients; however, there was no convincing evidence of an inappropriate blood pressure-PRA relationship as a prominent feature in the hypertensive patients. PRA did not correlate with blood volume. Patients with low PRA relative to sodium excretion (21% of hypertensive population) were consistently normovolemic, but tended to be older and excreted less (p less than 0.025) adrenaline than normal or high-PRA patients. The patient subgroup with high PRA relative to sodium excretion (11% of population) was hypovolemic (p less than 0.02); despite this, urinary sodium output was high (172 +/- 64 meq/24 hr). These data reveal no evidence for major roles of PRA, circulatory volume and free peripheral catecholamines in the maintenance of benign essential hypertension. Low-PRA essential hypertension is usually not a hypervolemic state, but may reflect diminished adrenergic activity, factors associated with aging and effects of a high systemic pressure. High PRA in benign essential hypertension may be at least partly a consequence of hypovolemia resulting from high blood pressure-induced sodium diuresis.