Fluid transport by cultured corneal epithelial cell layers

Background/aims-Fluid transport across the in vitro corneal epithelium is s hort lived, hence difficult to detect and characterise. Since stable rates of fluid transport across several cultured epithelial cell layers have been demonstrated, the behaviour of confluent SV40 transformed rabbit corneal e pithelial cells (tRCEC) grown on permeable supports was examined. Methods-Fluid transport was determined with a nanoinjector volume clamp; th e specific electrical resistance of the layers was 184 (SEM 9) Omega cm(2). tRCEC layers transported fluid (from basal to apical) against a pressure h ead of 3 cm H2O for 2-3 hours. Results-In the first hour, the rate of fluid transport was 5.2 (0.5) mu l/h /cm(-2) (n=23), which is comparable with that found in other epithelia. Flu id transport was completely inhibited in 15-30 minutes by either 100 mu M o uabain (n=6), 50 mu M bumetanide (n=6), or 1 mu M endothelin-1 (ET-1; n=6). Preincubation with 10 mu M BQ123 (an ETA receptor antagonist) obviated inh ibition by ET-1 (n=6). ET-1 also caused a 22% decrease in specific resistan ce. Conclusions-Fluid transport appears to depend on transepithelial Cl- transp ort since (1) their directions are the same (stroma-->tear), and (2) both b umetanide and ouabain inhibit it with similar time course. tRCEC appear use ful to investigate aspects of the physiology and pharmacology of fluid tran sport across this layer, including receptor mediated control of this proces s.