| Abstrakt: |
Effects of cyclooxygenase (COX) inhibitors on transport parameters of the frog corneal epithelium were studied. Epithelial cells of the intact cornea were impaled with microelectrodes. Under short-circuit current (Isc) conditions, 10?4 M ibuprofen (IBU) (non-specific COX inhibitor) or 5 × 10?5 M rofecoxib (COX-2 inhibitor) were added to the tear solution. With ibuprofen, Isc decreased by 1.0 from 3.1 mA/cm2; intracellular potential, Vo, depolarized by 14.2 from ?56.9 mV; IBU did not affect the transepithelial conductance, gt, or the apical membrane fractional resistance, fRo. With rofecoxib, Isc decreased by 0.9 from 4.3 mA/cm2; Vo depolarized by 18 from ?62.4 mV; gt significantly increased by 0.03 from 0.37 ms/cm2; and fRo decreased by 12 from 50. Basolateral membrane K+ and apical membrane Cl? partial conductances were studied by the ion substitution method. Depolarization of Vo by an increase in stromal K+ from 4 to 79 mM was smaller with IBU (17.5 mV) or rofecoxib (19.2 mV) than without the inhibitors (29.1 and 29.3 mV, respectively). Depolarization of Vo, by a decrease in tear Cl? from 81 to 8.1 mM, was abolished by the COX inhibitors. Decrease in Isc and Vo can be explained by a decrease in the K+ and Cl? conductances. Experiments with amphotericin B ruled out a major effect of the inhibitors on the Na+/K+ ATPase pump. [ABSTRACT FROM AUTHOR] |
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