Regulation of corneal epithelial intracellular pH.

Intracellular pH (pHi) can affect many cell functions including metabolic activity, protein synthesis, and cell growth rates. For the corneal epithelium these processes are important for maintenance of its barrier function and ion transport properties. This brief report reviews some of the recent findings from my laboratory, which describe basic ion transport mechanisms, e.g., Na+/H+ exchange and lactate-H+ cotransport, useful for regulating pHi in rabbit corneal epithelium. The effects of acid challenges, 5% CO2 (simulated eye closure), and hypoxia (simulated contact lens wear) on pHi are also examined. The 5% CO2 drops pHi by approximately 0.2 units with little or no recovery, indicating that steady-state pHi in vivo is reduced during eye closure. By contrast, hypoxia in vitro slowly raises pHi, approximately 0.1 units, partially due to the stimulation of lactate-H+ efflux.