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 hypertensi on. We examined patients with immunoglobulin A (IgA) nephropathy to determi ne whether this sensitivity appears before hypertension begins and whether this sensitivity is related to histological damage. Thirty-eight patients w ith IgA nephropathy followed a diet with an ordinary sodium level for I wee k and a sodium-restricted diet for I week, in random order, and were divide d into 3 groups by their systemic blood pressure on the diet with an ordina ry sodium level (optimal, < 120/< 80 mm Hg, n=15; normal to high-normal, 12 0 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 c alculated 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 s core for tubulointerstitial damage were higher in patients with normal to h igh-normal blood pressure or hypertension than in patients with optimal pre ssure. The sensitivity index was significantly correlated with glomeruloscl erosis (P=0.001) and tubulointerstitial damage (P=0.002). In patients with normal to high-normal pressure, sodium restriction lowered blood pressure t o the optimal range and decreased proteinuria. In patients with IgA nephrop athy, sodium sensitivity of blood pressure related to renal histological da mage appears before hypertension.