DETECTION OF A CIRCULATING INHIBITOR OF THE NA-K+-CL- COTRANSPORT SYSTEM IN PLASMA AND URINE AFTER HIGH-SALT INTAKE()

The aim of the study was to detect the presence of an endogenous Na+-K +-Cl- cotransport inhibitor factor in plasma and urine from salt-loade d subjects. Twenty-six essential hypertensive patients (13 men, 13 wom en) and 6 normotensive controls (2 men, 4 women) received a diet conta ining 260 mmol/day of NaCl tablets for 7 days. Human erythrocytes from healthy blood donors (using bumetanide-stimulated Li+ efflux) were us ed to test the inhibition of Na+-K+-Cl- cotransport by different plasm a and urine concentrations collected the last day of the salt-loaded p eriod. The addition of plasma and urine from salt-loaded subjects sign ificantly inhibited erythrocyte Na+-K+-Cl- cotransport (P <.001). No d ifferences were observed between hypertensive patients and normotensiv e controls. These results provide evidence of an Na+-K+-Cl- cotranspor t inhibitor factor in plasma and urine from salt-loaded humans, in con cordance with previous reports in salt-loaded rats.