Intrarenal hemodynamics in patients with essential hypertension.

Intrarenal hemodynamics were estimated clinically in essential hypertension. Two-week studies were performed in 30 patients with essential hypertension who were given a regular sodium diet in the first week and a sodium-restricted diet in the second week. Intrarenal hemodynamic parameters such as afferent arteriolar (preglomerular) resistance, efferent arteriolar resistance, and glomerular hydrostatic pressure were calculated from renal clearances and plasma total protein concentration measured on the last day of the regular sodium diet. Calculations were based on Gomez's equations with the assumption that the gross filtration coefficient of glomerular capillaries was normal. The increase in afferent arteriolar resistance (8,100 +/- 500 dyne.sec.cm-5) was significantly correlated with an elevation in mean arterial pressure (120 +/- 2 mm Hg), whereas glomerular pressure (56 +/- 1 mm Hg) and efferent arteriolar resistance (2,500 +/- 100 dyne.sec.cm-5) remained normal. The renal function curve (pressure-natriuresis relation) was drawn by plotting urinary sodium excretion on the y axis as a function of mean arterial pressure on the x axis, both of which were measured on the last 3 days of each week. The extrapolated x intercept (107 +/- 2 mm Hg) of the renal function curve was strongly correlated in a 1:1 fashion with the sum of the arterial pressure drop from the aorta to the renal glomeruli plus the opposing pressures against glomerular filtration at glomeruli (r = 0.7, p less than 0.001) on the regular sodium diet, suggesting that the difference between mean arterial pressure on the regular sodium diet and the extrapolated x intercept represented the effective filtration pressure across the glomerular capillaries on the regular sodium diet.(ABSTRACT TRUNCATED AT 250 WORDS)