Cardiovascular remodelling and red blood cell Li+/Na+ countertransport in patients with type 1 diabetes and essential hypertension

Patients with type 1 (insulin-dependent) diabetes may develop a specific cardiac disease characterized by functional and structural abnormalities. The pathogenesis of the cardiac disease is poorly understood but cardiac and renal complications may coexist. Patients with overt diabetic nephropathy have increased red cell Li+/Na+ countertransport (CT), which reflects abnormal kinetic properties of the red cell membrane Na+/H+ exchange. Since the activation of Na+/H+ exchange has a key role in cell proliferation and cell growth, as well as in the regulation of cell sodium and cell pH and in the renal reabsorption of Na+ and bicarbonate, we have looked for relationships between red cell Li+/Na+ CT, Na+/H+ exchange and cardiovascular remodeling in patients with type 1 diabetes, essential hypertension and idiopathic familiar cardiomyopathy. In type 1 diabetes the maximal velocity of Li+/Na+ CT is positively correlated with interventricular septum thickness and the left ventricular wall to lumen ratio. Similar results were obtained in patients with essential hypertension. In these patients an increased Li+/Na+ CT is also associated with severe and drug-resistant hypertension and with significant vascular remodelling, estimated by the minimal post-ischaemic vascular resistance in the calf. Finally, Li+/Na+ CT is negatively correlated with diastolic relaxation of the left ventricle in familiar hypertrophic cardiomyopathy. From these data it appears that widespread abnormal kinetic properties of Na+/H+ exchange, estimated by increased red cell Li+/Na+ CT, may have epistatic effects on the pathogenesis of cardiac complications of type 1 diabetes and essential hypertension.