Insulin and renal sodium retention in hypertension-prone men

Insulin-stimulated peripheral glucose uptake and insulin-induced renal tubular sodium reabsorption were investigated in normotensive men with a family history of hypertension (relatives, n = 35) compared with age- and body mass index-matched normotensive men with no family history of hypertension (controls, n = 23). The effect of insulin on the renin-aldosterone system was also studied. The euglycemic hyperinsulinemic clamp technique was used to measure peripheral glucose uptake (insulin sensitivity index). Renal clearance of 51Cr-labeled EDTA, sodium, and lithium was used to calculate fractional excretion of sodium and fractional proximal and distal tubular reabsorption of sodium before and during insulin infusion. The insulin sensitivity index was lower in relatives than in controls. Fractional excretion of sodium was reduced, and fractional proximal and distal tubular reabsorption of sodium were increased to the same extent in both groups during insulin infusion. Fractional distal tubular reabsorption of sodium was positively correlated to the reduction of serum potassium in all individuals. Plasma renin activity increased to the same extent in both groups, whereas plasma aldosterone was reduced only in controls. In conclusion, the impaired insulin-stimulated glucose uptake in peripheral tissues in normotensive sons of hypertensive families was accompanied by retained insulin-induced tubular sodium reabsorption. The lack of suppression of aldosterone secretion in these individuals may enhance sodium retention.