Heterogeneous derangement of cellular sodium metabolism in Bartter's syndrome. Description of two cases and review of the literature.

The basic tubular alteration present in Bartter's syndrome is still a subject of controversy. The possibility that a generalized defect in transmembrane ion transport underlies the disease has been extensively investigated. Previous evaluations of cellular sodium metabolism in Bartter's patients showed extremely variable findings. In the present study we have examined in red blood cells of two patients with Bartter's syndrome the intracellular Na+ and K+ concentrations, the activity of ouabain-sensitive Na+/K+ pump, furosemide sensitive Na+/K+ cotransport, Na+/Li+ countertransport, and the rate constant of Na+ and K+ passive permeability. We have compared these values with those of a control group. Ouabain-sensitive Na+/K+ pump activity was decreased in both patients, whereas Na+/Li+ countertransport was activated. One of the patients also exhibited markedly decreased intraerythrocyte K+ concentration and decreased furosemide-sensitive Na+/K+ cotransport. The other had increased Na+/K+ cotransport activity and Na+ passive permeability. Intracellular Na+ and passive permeability to K+ were normal in both subjects. Our results are partially consistent with previously reported observations, and indicate the existence of heterogeneous alterations of erythrocyte sodium transport systems in patients with Bartter's syndrome. Although some of these alterations could be secondary to the electrolyte metabolism derangements of this disease, others might be genetically transmitted and could cause the different renal tubular defects shown in Bartter's disease so far.