Effects of ethacrynic acid on endothelial function in human and rabbit corneas

Ethacrynic acid (ECA) has been used to increase outflow facility and lower intraocular pressure: when used topically or following intracameral injecti on. Our experiments evaluated the effect of EGA on corneal endothelial func tion (corneal swelling and endothelial permeability), cytoskeleton, and ult rastructure. Rabbit and human corneas were mounted in the in vitro specular microscope for endothelial perfusion of EGA (10(-3), 10(-4), 10(-5) M) add ed to GBR or BSS Plus. Corneal thickness was measured during the perfusion and a corneal swelling rate calculated. At the end of the perfusion, cornea s were fixed for electron microscopic evaluation (scanning and transmission electron microscopy [SEM, TEM]). Endothelial permeability was measured usi ng carboxyfluorescein, and endothelial F-actin was stained using bodipy-flu orescein phallacidin. ECA at 10(-5) M caused minimal corneal swelling and n o endothelial ultrastructural changes in rabbit corneas. After a 1 h lag ti me, comeas perfused with 10(-4) M ECA swelled at a rate of 28.1 +/- 4.7 mu m/h and endothelial cellular edema was evident. At 10(-3) M, ECA caused imm ediate corneal swelling (34.7 +/- 4.1 mu m/h) and significant endothelial u ltrastructural changes. ECA did not significantly affect endothelial permea bility to carboxyfluorescein. Human corneas perfused with 10(-3) M ECA swel led at a rate of 22.5 +/- 4.3 vs. BSS Plus control (-5.5 +/- 4.6 mu m/h), w hereas 10(-4) M ECA caused no corneal swelling compared to BSS Plus. Signif icant ultrastructural changes were observed when human corneas were perfuse d with 10(-3) M EGA. These studies show that ECA can cause corneal swelling and endothelial ultrastructural changes. The endothelial barrier remains i ntact, however. ECA at 10(-4) M in human and 10(-5) M in rabbit are well to lerated by the corneal endothelium.