A Preliminary Investigation into the Opacifying Effects In Vitro of Compounds with Varying Numbers of Nitrogen-containing Groups using Isolated Porcine Corneas

Abstract

Isolated intact porcine corneas were incubated for 4 hours with solutions of various compounds, bathing either the epithelial or endothelial surface or both surfaces, and the resulting opacities were measured. All compounds were tested at 5 x 10-4 M, 5 x 10-3 M, 5 x 10 2M and 1 x 10 1M. Solutions of pilocarpine HC1, carteolol HC1 and timolol maleate (which contain 2 or 4 nitrogens) caused a greater opacity when applied to the endothelial surface than when applied to both the endothelial and epithelial surfaces. By contrast, solutions of sodium lauryl sulphate, befunolol HC1 and dibucaine HC1 (which contain 0, 1 or 3 nitrogens) caused a greater opacity when applied to both surfaces than when applied to the endothelial surface alone. In both groups, there was a good correlation between the greatest opacities and the osmolalities of the various solutions. The difference in responses to the two groups of compounds may be related to the number of nitrogen atoms in the molecules. It is suggested that there is something in the porcine corneal epithelium which inhibits the uptake of compounds containing 2 or 4 nitrogens. Alternatively, in the presence of these compounds, the epithelium may be able to actively pump out water that has entered by diffusion. We wish to thank Mrs A.M. Northover for her linguistic assistance, and the local slaughterhouse at Koriyama-shi for the supply of fresh porcine eyes.