NA- COTRANSPORT IS A MARKER OF DISTAL TUBULAR FUNCTION IN ESSENTIAL-HYPERTENSION(,K+,CL)

Objective: To analyze the natriuretic and diuretic response to frusemi de in 33 male essential hypertensive patients as a function of basal r enal sodium handling and erythrocyte transport system. Methods: The na triuretic and diuretic response to an oral dose of frusemide (25 mg) w as assessed with a simplified method. Urinary sodium and water excreti on were measured in the basal state and every 30 min after the frusemi de dose for 240 min. Basal 24h urinary sodium and water excretion, Na,K+,Cl- cotransport and Li+-Na+ countertransport were measured 24h bef ore the test. Results: There was a high ly significant correlation bet ween the natriuretic and diuretic response to frusemide and Na+,K+,Cl- cotransport and Li+-Na+ countertransport. After a multiple regression analysis the natriuretic and diuretic response to frusemide was not c orrelated with indices of proximal tubular function (Li+-Na+ countertr ansport, fractional uric acid excretion and the ratio of fractional so dium excretion to fractional uric acid excretion). Conclusion: These r esults support the hypothesis that erythrocyte Nat,K+,Cl(-)cotransport is a marker of distal tubular function.