Evidence for amiloride-sensitive sodium channels in alveolar epithelial cells
R M Russo1, R L Lubman, E D Crandall
1Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, University of Southern California, Los Angeles 90033.
The American Journal of Physiology
|April 1, 1992
Summary
Alveolar epithelial cells primarily use sodium channels for sodium entry, facilitating fluid balance in the lungs. This research identifies key ion transport mechanisms essential for maintaining alveolar fluid homeostasis.
Area of Science:
- Cell Biology
- Respiratory Physiology
- Ion Transport
Background:
- Alveolar epithelium maintains fluid-free air spaces through vectorial transport.
- Active sodium transport by alveolar pneumocytes is crucial for this process.
- Understanding apical sodium entry mechanisms is key to elucidating this function.
Purpose of the Study:
- To investigate the specific mechanisms of sodium entry into rat alveolar epithelial cells.
- To determine the contribution of various ion transporters to apical sodium uptake.
- To identify the primary pathway for sodium entry in alveolar epithelial cells.
Main Methods:
- Primary culture of rat alveolar epithelial cells.
- Measurement of 22Na uptake over time.
- Assessment of inhibitor effects on sodium uptake, including amiloride and its analogues, bumetanide, and glucose absence.
Main Results:
- 22Na uptake increased with time in cultured cells.
- Sodium uptake was significantly inhibited by amiloride and benzamil.
- Uptake was not affected by amiloride analogues targeting Na(+)-H+ antiporter, bumetanide, or absence of glucose.
Conclusions:
- Sodium entry into alveolar epithelial cells predominantly occurs via sodium channels.
- Na(+)-H+ antiport, Na(+)-K(+)-2Cl- cotransport, and Na(+)-glucose cotransport do not significantly contribute to sodium uptake.
- Sodium channels are likely the major mechanism for sodium entry, supporting active extrusion and fluid reabsorption from alveolar spaces.
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