Selective effects of bumetanide on chloride transport in bullfrog cornea.
Frog corneas were mounted in a modified Ussing chamber and short-circuit current (SCC) and unidirectional Cl fluxes were measured. Bumetanide, a loop diuretic, at concentrations as low as 10(-7) M, reduced the SCC 29%. At 10(-5) M, bumetanide reduced the SCC 96% and increased transcorneal electrical resistance 20-51%. The forward Cl flux declined from 0.71 +/- 0.04 to 0.20 +/- 0.03 mueq/h.cm2 (n, 7), while, in separate experiments, the backward Cl flux did not change significantly (from 0.22 +/- 0.03 to 0.23 +/- 0.04; n, 7). When corneas were mounted in Cl-free Ringer and the net Na transport was stimulated with amphotericin B, 10(-5) M bumetanide had no effect on the SCC. In separate experiments the effect of 10(-5) M bumetanide on the O2 consumption was measured in a stirrer bath assembly. Bumetanide decreased the O2 consumption from 352 +/- 14 to 297 +/- 19 microliter/h.cm2 (significantly different from sham-treated controls). This decrease was similar to that obtained with furosemide or when Cl was removed from the bathing medium. We infer from these results that bumetanide is a selective inhibitor of active Cl transport in the bullfrog cornea.
D000818:Animals; D001001:Anura; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism* / Q000502:physiology; D004232:Diuretics / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008564:Membrane Potentials; D010101:Oxygen Consumption / Q000187:drug effects; D011458:Prostaglandins E / Q000494:pharmacology; D011892:Rana catesbeiana
D002712:Chlorides; D004232:Diuretics; D011458:Prostaglandins E; D002034:Bumetanide; D000001:Calcimycin