1. Intrarenal pressure, estimated by measurement of wedged renal vein pressure, was elevated in patients with essential hypertension. Despite increased afferent arteriolar resistance, glomerular pressure was elevated indicating that the higher systemic pressure in essential hypertension is transmitted beyond the arterioles and accounts for elevation of intrarenal pressure.
2. During hypertonic saline loading in hypertensives, renal arteriolar resistance falls, resulting in further increase in intrarenal pressure. Increments in intrarenal pressure paralleled increases in sodium excretion in patients with essential hypertension during the exaggerated natriuresis and in normotensive subjects after the prolonged infusion of hypertonic saline.
3. The marked increase in intrarenal pressure which appears to be responsible for exaggerated natriuresis in essential hypertension is attributable to an altered (exaggerated) response of the renal arterioles. The data suggest that elevated intrarenal pressure may play a role in the regulation of sodium balance in patients with essential hypertension.