Sodium restriction corrects hyperfiltration of diabetes.

The effect of a low-sodium diet on the abnormal glomerular hemodynamics of early diabetes was studied in rats. Starting 5 to 7 days after onset of streptozotocin-induced insulin-dependent diabetes mellitus (IDDM), rats were fed a low-sodium diet for 4-5 days. Normal rats fed the same diet served as controls. Micropuncture measurements were made during a control period, followed by a second period when saralasin was infused into the left renal artery. During the first period, single-nephron glomerular rate (SNGFR), glomerular plasma flow (QA), glomerular blood flow (SNBF), filtration fraction (SNFF), and glomerular hydraulic pressure (PG) in the diabetic rats were not significantly different from the normal controls. Saralasin infusion resulted in striking increases in SNGFR, QA, SNBF, and Kf, and significant decreases in SNFF, PG, and delta P. The responses to saralasin imply that the low-sodium diet resulted in ANG II-mediated vascular constriction at pre- and postglomerular sites, and probably the glomerular mesangial cells as well. Our observations suggest that the abnormally elevated glomerular blood flow and filtration rate of early IDDM can be corrected by a low-sodium diet via stimulation of endogenous ANG II.