Transport of fluid by lens epithelium

We report for the first time that cultured lens epithelial cell layers and rabbit lenses in vitro transport fluid. Layers of the alpha TN4 mouse cell line and bovine cell cultures were grown to confluence on permeable membr ane inserts. Fluid movement across cultured layers and excised rabbit lenses was determined by volume clamp (37 degrees C). Cultured layers transported fluid from their basal to their apical sides against a pressure head of 3 cmH(2)O. Rates were (in mu l . h(-1) . cm(-2)) 3.3 +/- 0.3 for alpha TN4 cells (n = 27) and 4.7 +/- 1.0 for bovine layers (n = 6). Quinidine, a blocker of K+ channels, and p-chloromercuribenzenesulfonate and HgCl2, inhibitors of aquaporins, inhibited fluid transport. Rabbit lenses transported fluid from their anterior to their posterior sides; against a 2.5-cmH(2)O pressure head at 10.3 +/- 0.62 mu l . h(-1) . lens(-1) (n = 5) and along the same pressure head at 12.5 +/- 1.1 mu l . h(-1) . lens(-1) (n = 6). We calculate that this flow could wash the lens extracellular space by convection about once every 2 h and therefore might contribute to lens homeostasis and transparency.