May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Evaluating the Expression and Function of Carbonic Anhydrase IV in Bovine Corneal Endothelial Cells
Author Affiliations & Notes
  • X. Sun
    School of Optometry, Indiana University, Bloomington, IN
  • J.A. Bonanno
    School of Optometry, Indiana University, Bloomington, IN
  • Footnotes
    Commercial Relationships  X. Sun, None; J.A. Bonanno, None.
  • Footnotes
    Support  EY08834
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 427. doi:
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      X. Sun, J.A. Bonanno; Evaluating the Expression and Function of Carbonic Anhydrase IV in Bovine Corneal Endothelial Cells . Invest. Ophthalmol. Vis. Sci. 2004;45(13):427.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Abstract: : Purpose: Previous functional studies have revealed that membrane–associated carbonic anhydrase IV (CA IV) is expressed in bovine corneal endothelial cells (BCEC). However, the molecular study of CA IV has not been reported in BCEC. In this study, we further tested the molecular expression, distribution and function of CA IV in BCEC. Methods: RT–PCR and sequencing were performed to identify the mRNA expression of CA IV in cultured BCEC. In addition, immunoblot analysis was used to further demonstrate the protein expression of CA IV. Immunofluorescence and confocal microscopy determined the distribution of CA IV in BCEC. Intracellular pH was measured with the pH sensitive fluorescent dye BCECF. This was used to measure apical CO2 flux–induced intracellular pH changes following inhibition of CA IV activity using extracellular carbonic anhydrase inhibitors (CAIs) or siRNA knockdown of CA IV. Results: RT–PCR showed a single band at the predicted size. Sequencing analysis further confirmed the identity of CA IV. Immunoblot analysis showed a positive band at ∼40 kD, which is consistent with other studies. Immunofluorescence and confocal microscopy demonstrated that CA IV in BCEC is localized at the apical membrane. Transfection of 30 nM siRNA specific for CA IV reduced CA IV protein expression by more than 90%. 10 µM benzolamide significantly decreased apical CO2 efflux–induced intracellular pH changes by 48 ± 3 % relative to the control (n=15). Conclusion: Membrane–associated carbonic anhydrase IV is functionally expressed in the apical membrane of BCEC. CO2 diffusion may contribute to apical HCO3flux through the action of carbonic anhydrase IV, thereby increasing HCO3 efflux from the apical membrane.

Keywords: ion transporters • PH regulation/protons • cornea: endothelium 
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