Studies on the expression of mRNA for anion transport related proteins in corneal endothelial cells

Purpose. Chloride and bicarbonate are necessary for maintenance of fluid tr ansport by the corneal endothelium, however there is little information on the identity of anion transport proteins that could serve as anion efflux m echanisms in endothelial cells. Therefore, we ask whether mRNA for the anio n transport related proteins, CFTR, CLC-2, ClC-3, ClC-5 and AE2, are expres sed in human, bovine or rabbit corneal endothelium. Methods. RT-PCR was performed for CFTR, CLC-2, ClC-3, ClC-5 and AE2 using t otal RNA from fresh human, bovine and rabbit corneal endothelium as well as cultured bovine corneal endothelial cells (CBCEC). Specificity of PCR prod ucts was confirmed by sequencing. Results. RT-PCR analysis gave positive bands at the predicted size for CLC- 3 and CLC-5 from fresh human, rabbit and bovine as well as CBCEC. However, for CLC-2, no band was apparent around the predicted size from fresh and cu ltured corneal endothelium. A band at the predicted size was obtained for C FTR from fresh human, rabbit and bovine endothelium, as well as from CBCEC. RT-PCR analysis for AE2 produced specific bands from fresh human, rabbit a nd bovine corneal endothelium, but no positive band was obtained from CBCEC . Sequencing analysis further confirmed the identities of CLC-3, CLC-5, CFT R and AE2 in corneal endothelium. Conclusions. CFTR, CLC-3 and ClC-5 are expressed in fresh and cultured corn eal endothelial cells. However, consistent with previous immunoblots studie s, AE2 is only expressed in fresh corneal endothelium. These results have i mplications for modeling possible apical anion efflux mechanisms in corneal endothelium.