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Inner medullary collecting duct Na(+)-H+ exchanger
K S Hering-Smith1, E J Cragoe, D Weiner
1Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
The American Journal of Physiology
|June 11, 1991
Summary
Inner medullary collecting duct cells utilize sodium-hydrogen (Na(+)-H(+)) exchange for intracellular pH regulation. This process is basolateral, present in nearly all cells, and distinct from Na(+)-independent H(+) extrusion.
Area of Science:
- Nephrology
- Cell Physiology
- Molecular Biology
Background:
- Inner medullary collecting duct (IMCD) cells play a crucial role in renal acid-base balance.
- Sodium-hydrogen (Na(+)-H(+)) exchange is a key mechanism for regulating intracellular pH in various cell types.
- Understanding Na(+)-H(+) exchange in IMCD cells is vital for comprehending renal function.
Purpose of the Study:
- To characterize the properties of Na(+)-H(+) exchange in cultured IMCD cells.
- To determine the cellular localization and functional characteristics of this transport system.
- To compare Na(+)-H(+) exchange in IMCD cells with that in renal proximal tubule cells.
Main Methods:
- Cell culture of IMCD and renal proximal tubule cells.
- Intracellular pH measurements using image analysis techniques.
- Assessment of Na(+)-H(+) exchange kinetics and inhibitor sensitivity.
Main Results:
- Na(+)-H(+) exchange operates effectively at both 37°C and 25°C in IMCD cells.
- Nearly all IMCD cells express Na(+)-H(+) exchange, primarily on the basolateral membrane.
- Na(+)-H(+) exchange in IMCD cells shares kinetic similarities (Km for Na+, Ki for EIPA) with proximal tubule cells, despite differing polarity.
Conclusions:
- IMCD Na(+)-H(+) exchange functions primarily in intracellular pH regulation, not transepithelial transport.
- The basolateral localization and widespread expression suggest a housekeeping role for pH homeostasis.
- Functional similarities between IMCD and proximal tubule Na(+)-H(+) exchange indicate conserved molecular mechanisms despite distinct cellular roles and polarity.