Sodium sensitivity of blood pressure appearing before hypertension and related to histological damage in immunoglobulin A nephropathy

Patients with renal parenchymal disease exhibit sodium-sensitive hypertension. We examined patients with immunoglobulin A (IgA) nephropathy to determine whether this sensitivity appears before hypertension begins and whether this sensitivity is related to histological damage. Thirty-eight patients with IgA nephropathy followed a diet with an ordinary sodium level for I week and a sodium-restricted diet for I week, in random order, and were divided into 3 groups by their systemic blood pressure on the diet with an ordinary sodium level (optimal, < 120/< 80 mm Hg, n=15; normal to high-normal, 120 to 139/80 to 89 mm Hg, n=18; hypertensive, greater than or equal to 140/ greater than or equal to 90 mm Hg, n=5). The sodium sensitivity index was calculated as the reciprocal of the slope of the pressure-natriuresis curve drawn by linkage of 2 datum points obtained during the different diets. The scores for glomerulosclerosis and tubulointerstitial damage were evaluated semiquantitatively. The sensitivity index, glomerulosclerosis score, and score for tubulointerstitial damage were higher in patients with normal to high-normal blood pressure or hypertension than in patients with optimal pressure. The sensitivity index was significantly correlated with glomerulosclerosis (P=0.001) and tubulointerstitial damage (P=0.002). In patients with normal to high-normal pressure, sodium restriction lowered blood pressure to the optimal range and decreased proteinuria. In patients with IgA nephropathy, sodium sensitivity of blood pressure related to renal histological damage appears before hypertension.