Cornea endothelial bicarbonate fluxes following preservation in solutions of varying composition

Numerous modifications have been made in MK solution, primarily concerned with alterations in both bicarbonate concentration and PCO2. Variations of the solutions from high bicarbonate to low bicarbonate and either high or low PCO2 were made which resulted in a decreased net bicarbonate flux across the endothelium after a 3-day storage period. Even with drastic changes in the storage solution there was a relatively small change in the net bicarbonate flux. Higher passive fluxes were found at a pH above 8, and a higher net flux with a bicarbonate concentration of 17.5 nM or higher. Variation in PCO2 made little difference to the net endothelial fluxes; when a high PCO2 was used, there was a concurrent elevation of PO2 in the storage solution, but no beneficial effect was found on the endothelial transport system. It was apparent that a good storage solution contained a buffer (bicarbonate was better than phosphate) and 5% dextran and was at a neutral pH (between 7 and 8).