Erythrocyte sodium-hydrogen exchange and microalbuminuria in type I diabetes

OBJECTIVE - To evaluate the relationship between sodium-hydrogen (Na+/H+) exchange and microalbuminuria (an abnormal urinary albumin/creatinine ratio in morning collections) in IDDM patients. RESEARCH DESIGN AND METHODS - Amiloride-sensitive H+ efflux from cells acid loaded at pH 6.5 (defined as erythrocyte Na+/H+ exchange) was measured in normotensive IDDM patients with microalbuminuria and normal renal function (n = 16, serum creatinine <106.1 mu mol/l) and compared with both matched uncomplicated normoalbuminuric diabetic subjects and normal subjects (n =16 each). RESULTS - Erythrocyte Na+/H+ exchange was elevated to a similar extent in diabetic patients with and without microalbuminuria. Blood pressure and lipids were normal in both diabetic groups. Daily insulin requirement, blood glucose, and glycated hemoglobin were higher and retinopathy more frequent in microalbuminuric patients. CONCLUSIONS - The abnormal erythrocyte Na+/H+ exchange of type I diabetic patients was unrelated to microalbuminuria and could not be ascribed to hypertension or dyslipidemia. Furthermore, the degree of metabolic control seemed to influence the progression of diabetic nephropathy, but not the abnormal antiport activity. The data imply that Na+/H+ exchange is an unlikely marker of nephropathy in type I diabetic patients.