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Abstract
Ethacrynic acid (ECA) has been used to increase outflow facility and lower intraocular pressure when used topically or following intracameral injection. Our experiments evaluated the effect of ECA on corneal endothelial function (corneal swelling and endothelial permeability), cytoskeleton, and ultrastructure. Rabbit and human corneas were mounted in the in vitro specular microscope for endothelial perfusion of ECA (10−3, 10−4, 10−5 M) added to GBR or BSS Plus. Corneal thickness was measured during the perfusion and a corneal swelling rate calculated. At the end of the perfusion, corneas were fixed for electron microscopic evaluation (scanning and transmission electron microscopy [SEM, TEM]). Endothelial permeability was measured using carboxyfluorescein, and endothelial F-actin was stained using bodipy-fluorescein phallacidin. ECA at 10−5 M caused minimal corneal swelling and no endothelial ultrastructural changes in rabbit corneas. After a 1 h lag time, corneas perfused with 10−4 M ECA swelled at a rate of 28.1 ± 4.7 μm/h and endothelial cellular edema was evident. At 10−3 M, ECA caused immediate corneal swelling (34.7 ± 4.1 μm/h) and significant endothelial ultrastructural changes. ECA did not significantly affect endothelial permeability to carboxyfluorescein. Human corneas perfused with 10−3 M ECA swelled at a rate of 22.5 ± 4.3 vs. BSS Plus control (-5.5 ± 4.6 μm/h), whereas 10−4 M ECA caused no corneal swelling compared to BSS Plus. Significant ultrastructural changes were observed when human corneas were perfused with 10−3 M ECA. These studies show that ECA can cause corneal swelling and endothelial ultrastructural changes. The endothelial barrier remains intact, however. ECA at 10−4 M in human and 10−5 M in rabbit are well tolerated by the corneal endothelium.