Increased platelet sodium-proton exchange rates in insulin-dependent (type 1) diabetic patients with nephropathy and hypertension.

In order to assess the potential role of the plasma membrane sodium-proton (Na+/H+) exchanger in the pathogenesis of diabetic nephropathy, we investigated 32 insulin dependent (type 1) diabetic patients and 21 control subjects. We tested the Na+/H+ exchange as the rate of amiloride sensitive and sodium dependent volume gain of platelets suspended in sodium propionate. Patients with diabetic nephropathy had significantly increased rates of Na+/H+ exchange (0.31 +/- 0.06 s-1 x 10(-2)) when compared to those without nephropathy (0.24 +/- 0.07, p less than 0.05) or to a control group (0.23 +/- 05, p less than 0.05). Nine patients who were classified as hypertensive had a highly significant increase in the Na+/H+ exchange rates when compared to 23 non-hypertensive diabetic patients: 0.33 +/- 0.04 versus 0.24 +/- 0.06 (p less than 0.001). There was no significant correlation between the Na+/H+ exchange rates and age, diabetes duration, glycated hemoglobin or fructosamine levels on the day of the test. In summary, the data presented here demonstrate an increase in the Na+/H+ exchange rate in insulin-dependent diabetic patients with nephropathy and hypertension.