INFLUENCE OF IONS, OUABAIN, PROPRANOLOL AND AMILORIDE ON THE TRANS-EPITHELIAL POTENTIAL AND RESISTANCE OF RABBIT CORNEA

By means of in vitro ion substitution experiments the potential difference and resistance dependency of rabbit corneal epithelium on Na+, K+ and Cl- activities have been established at the tear side as well as at the aqueous side. In normal conditions only a K+ selectivity at the aqueous side of the epithelium exists and a Na+ and Cl- selectivity at the tear side. The tear side was also K+ selective at K+ activities greater than 28 mm. In Cl- Ringer bathing solutions a rectifying current-voltage relationship is obtained. Ouabain gives rise to a two phase decrease in potential from 29·9±2·4 to 22·9±2·1 to 14·4±1·7 mV (n = 9). In the first phase the resistance changes from 3·7±0·4 to 4·0±0·4 kΩcm2 (n = 9) and in the second phase R decreased to 1·3±0·1 kΩcm2 (n = 9). After ouabain the Na+ selectivity has disappeared and the Cl- permeability has increased. The current-voltage relationship after ouabain has become linear. Amiloride induced a reversible change in resistance from 3·5±0·6 to 4·8±0·8 kΩcm2 accompanied by a depolarization from 29·1±2·7 to 22·6±1·5 mV (n = 4), moreover the rectifying properties as exhibited in control cornea are not affected by amiloride. A voltage dependent Cl--conductivity of the tear side membranes of the corneal epithelium can be postulated as well as a voltage independent Cl--conductivity that can be induced by ouabain. The ouabain effects are inhibited by propranolol. © 1979.