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Lactate-proton cotransport in rabbit corneal epithelium
1Morton D. Sarver Center for Cornea and Contact Lens Research, University of California, School of Optometry, Berkeley 94720.
Current Eye Research
|July 1, 1990
Summary
Rabbit corneal cells utilize lactate-H+ cotransport to manage intracellular pH during low-oxygen conditions, as demonstrated by pH dye measurements and inhibitor studies.
Area of Science:
- Physiology
- Cell Biology
- Biochemistry
Background:
- The corneal epithelium's ability to regulate intracellular pH (pHi) is crucial for its function.
- Membrane transport mechanisms, such as lactate-H+ cotransport, are potential regulators of pHi.
Purpose of the Study:
- To investigate the presence and function of lactate-H+ cotransport in rabbit corneal epithelium.
- To determine the role of this cotransporter in pHi regulation, particularly during hypoxia.
Main Methods:
- Rabbit corneal explants were loaded with the pH-sensitive dye BCECF.
- Intracellular pH was measured using fluorescence microscopy.
- The effects of lactate perfusion and hypoxia on pHi were assessed in the presence and absence of specific cotransporter inhibitors.
Main Results:
- Lactate perfusion reversibly decreased intracellular pH, indicating proton influx.
- This proton influx followed saturating kinetics (Km = 10.7 mM, Vmax = 10.2 mM/min).
- Specific inhibitors (CHC, H2DIDS, LAIE, Mersalyl acid) significantly blocked lactate-induced proton influx, confirming lactate-H+ cotransport.
- Hypoxia-induced alkalinization was partially inhibited by these agents, suggesting cotransporter involvement in pHi homeostasis.
Conclusions:
- Lactate-H+ cotransport is present and functional in the rabbit corneal epithelium.
- This mechanism plays a significant role in regulating intracellular pH, especially under hypoxic stress.