Abstract.
Although bicarbonate transport in corneal endothelium has been suggested to be coupled to Na+, the underlying molecular mechanism has not been clarified. In the present study we investigated whether a recently cloned Na+-HCO3 – cotransporter (NBC-1) is responsible for this process, and, if so, whether the endothelium expresses a separate isoform or one of the other two isoforms that have recently been identified (kNBC-1 from kidney and pNBC-1 from pancreas). Using primers designed for specific and common regions we demonstrated by reverse transcriptase polymerase chain reaction (RT-PCR) that both kNBC-1 and pNBC-1 are expressed in cultured human corneal endothelial cells. In addition functional studies with a pH-sensitive fluorescence probe were performed. In the presence of HCO3 –/CO2 a pH regulatory process was demonstrated which depends on the presence of Na+ and membrane potential, but is independent of Cl– and is inhibited by the disulfonic stilbene DIDS. These results support the presence of NBC-1 as the major bicarbonate transport system in corneal endothelium.
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Received after revision and accepted: 19 May 1999
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Usui, T., Seki, G., Amano, S. et al. Functional and molecular evidence for Na+-HCO3 – cotransporter in human corneal endothelial cells. Pflügers Arch – Eur J Physiol 438, 458–462 (1999). https://doi.org/10.1007/s004249900081
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DOI: https://doi.org/10.1007/s004249900081