Changes in renal function in essential hypertension

Abstract

Studies of renal hemodynamics, plasma renin activity (PRA), plasma aldosterone, and water and sodium excretion were performed in 171 patients with essential hypertension and 61 normotensive subjects. The para-amino hippurate clearance (C PAH) was usually normal or moderately reduced in those with benign hypertension and markedly depressed in those with malignant hypertension. The PAH extraction ratio was normal or slightly reduced in the patients with benign hypertension and moderately impaired in those with low C PAH indicating that a disproportionate decrease in cortical flow occurred only in the latter. The c pah did not correlate Inversely with the mean blood pressure in the patients with benign hypotension. Reexamination of untreated patients after an average of 28 1 2 months revealed a decrease in renal plasma flow but no further increase in blood pressure. These findings suggest that in uncomplicated hypertension the increase in blood pressure is not caused by renal circulatory disturbances. PRA was unrelated to renal hemodynamics in benign hypertension. In malignant hypertension, it was inversely correlated with the renal plasma flow. Under mild loading with isotonic saline solution, the fractional water excretion correlated with the blood pressure. Sodium excretion was neither related to the blood pressure nor to the estimated peritubular oncotic pressure, but correlated inversely with plasma aldosterone. These observations provide no support for the causative role of a primary disturbance in sodium excretion in essential hypertension.