Chloride concentrations in the corneal epithelium and stroma from different species

Using ion chromatography, the concentration of chloride in the corneal stroma and epithelium of ox, pig and rabbit was measured to detect possible species differences. In all three species, the chloride concentration in the stroma was found to be very similar, i.e. 363 +/- 14 mmol kg-1 dry wt in ox, 364 +/- 18 mmol kg-1 dry wt in pig and 358 +/- 24 mmol kg-1 dry wt in rabbit. In contrast, a substantially higher concentration of 232 +/- 33 mmol kg-1 dry wt was found in the corneal epithelium of rabbit in comparison to the values determined in the same tissue of ox, i.e. 137 +/- 4 mmol kg-1 dry wt and of pig, i.e. 128 +/- 24 mmol kg-1 dry wt. Using the results obtained previously for the extracellular volume (Midelfart 1988), an intracellular chloride concentration of 25 +/- 2 mmol kg-1 H2O was calculated in the bovine corneal epithelium. The results obtained in this study indicate that species differences are considered as important in studies of ion transport mechanisms in the cornea.