Relationships Between Sodium Clearance, Plasma Renin Activity, Plasma Aldosterone, Renal Hemodynamics and Blood Pressure in Essential Hypertension

Renal hemodynamics, plasma renin activity (PRA), plasma aldosterone (PA) and sodium excretion were studied in essential hypertension. PAH clearance (CPAH) and glomerular filtration rate (GFR) were normal or increased in early hypertension and depressed at later stages, especially in malignant cases. The PAH extraction ratio was depressed only in patients with low CPAH values. CPAH did not correlate inversely with blood pressure in benign hypertension. Later reexamination of untreated patients revealed a decrease in CPAH, but no further increase in blood pressure. Antihypertensive treatment prevented the decrease in CPAH. Patients with essential hypertension showed no abnormality in basal sodium excretion, plasma aldosterone, plasma renin activity and the sodium: aldosterone relationship. Basal sodium clearance did not correlate with GFR and the fractional sodium excretion was not pressure-dependent. When clearance determinations and measurements of PA and PRA were performed simultaneously under standardized conditions, PA and PRA were correlated inversely with CPAH and GFR. There was no relationship between PA or PRA and the blood pressure. Unless adefective release of renal prostaglandins and/or kinins could be shown to be responsible for the increase in systemic blood pressure, there is no evidence for a primary renal disturbance in essential hypertension.