OBJECTIVE - To evaluate the relationship between sodium-hydrogen (Na+/
H+) exchange and microalbuminuria (an abnormal urinary albumin/creatin
ine ratio in morning collections) in IDDM patients. RESEARCH DESIGN AN
D METHODS - Amiloride-sensitive H+ efflux from cells acid loaded at pH
6.5 (defined as erythrocyte Na+/H+ exchange) was measured in normoten
sive 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 highe
r and retinopathy more frequent in microalbuminuric patients. CONCLUSI
ONS - The abnormal erythrocyte Na+/H+ exchange of type I diabetic pati
ents was unrelated to microalbuminuria and could not be ascribed to hy
pertension or dyslipidemia. Furthermore, the degree of metabolic contr
ol seemed to influence the progression of diabetic nephropathy, but no
t the abnormal antiport activity. The data imply that Na+/H+ exchange
is an unlikely marker of nephropathy in type I diabetic patients.