Effect of bicarbonate-free balanced salt solutions on fluid pump and endothelial morphology of rabbit corneas in-vitro.

Corneas from young adult albino rabbits were exposed, in-vitro, to various bicarbonate-free balanced salt solutions under an applied hydrostatic pressure of 20 cmH2O at 35 degrees C for up to 4.5 h. The solutions were buffered with a HEPES-MOPS mixture, phosphate salts or acetate-citrate salts (pH 7.1-7.4). All of these solutions support a net fluid pump activity attributed to the corneal endothelium although the net fluid pump rates were less than those measurable with a bicarbonate-buffered, CO2-equilibrated Ringer solution. Evaluation of the endothelia by scanning electron microscopy revealed no evidence of any acute toxic effect of the balanced salt solutions. Morphometric analyses of cell size and shape revealed a normal mosaic for endothelia exposed to commercial balanced salt solution for 5 h. The results further indicate that exogenous bicarbonate is not required for the net fluid pump function of the mammalian corneal endothelium.