In Bartter's syndrome, the defective renal tubular transport has been postulated to be a manifestation of a more generalized membrane abnormality. To explore this possibility, sodium concentration, ouabain-sensitive (pump transport), ouabain-resistant but furosemide-sensitive (Na-K-Cl cotransport), and ouabain- and furosemide-resistant (passive transport) 22Na effluxes were measured in erythrocytes obtained from nine patients with Bartter's syndrome before and during correction of hypokalemia. Intracellular [Na+] in erythrocytes obtained from nine patients with Bartter's syndrome was significantly (P less than 0.001) higher than that in 30 normal controls (11.8 +/- 1.8 vs. 7.3 +/- 1.4 mmol/liter cells). Pump transport and Na-K-Cl cotransport 22Na effluxes were significantly (P less than 0.01) increased, whereas the rate constant for these effluxes as well as for passive 22Na efflux did not differ from normal. Correction of hypokalemia and maintenance of a normal serum potassium decreased intracellular [Na+] to 8.2 +/- 1.8 mmol/liter cells, a normal value, and corrected the ouabain-sensitive and furosemide-sensitive 22Na effluxes. The results indicate that exposure of erythrocytes to a low potassium environment is responsible for the high intracellular [Na+] and, in turn, the high sodium efflux in Bartter's syndrome. The normal sodium efflux observed during correction of hypokalemia and the consistently normal rate constants for all three efflux parameters measured suggest that intrinsic sodium transport processes in erythrocytes are normal in Bartter's syndrome.
J M Korff, A W Siebens, J R Gill Jr