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 × 10–2) when compared to those without nephropathy (0.24 ± 0.07, p < 0.05) or to a control group (0.23 ± 05, p < 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 < 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