ERYTHROCYTE NA- COTRANSPORT AND KIDNEY-FUNCTION IN ESSENTIAL-HYPERTENSION(,K+,CL)

Objective:To determine whether essential hypertensive patients with hi gh Na+,K+,Cl-cotransport (COT) display alterations of some indices of kidney tubular reabsorption similar to those observed in Milan hyperte nsive (MHS) rats, which have high COT in both erythrocytes and kidney tubular cells, and hypertension caused by a primary increase of tubula r reabsorption. Design: Two sets of experiments were performed. First, renal function in two subgroups of hypertensive patients (one with 'h igh' and one with 'normal' COT was compared with that in normotensive controls. Secondly, the natriuretic and diuretic effects of a single o ral dose of frusemide (25 mg) were analysed in six high- and in six no rmal-COT hypertensive patients. Results: Compared with normotensives a nd with normal-COT hypertensives, high-COT hypertensives had lower fra ctional uric acid excretion and plasma renin activity with similar glo merular filtration rate and urinary sodium and potassium excretion. CO T was negatively correlated with fractional uric acid excretion in the essential hypertensive patients but not in the normotensives. The diu retic natriuretic response to frusemide was much higher in high- than in normal-COT hypertensives. Conclusion: These results are consistent with the hypothesis that patients with high COT have abnormal renal ha ndling of sodium similar to that observed in MHS rats.