title: Open-circuit sodium and chloride fluxes across isolated opercular epithelia from the teleost Fundulus heteroclitus.
abstract: 1. The Na+ and Cl- fluxes across opercular epithelia from sea water-adapted Fundulus heteroclitus were measured in vitro under open-circuit conditions while bathed on the mucosa with sea water and the serosa with Ringer solution. 2. The mean predicted Na+ flux ratio was 0.94 +/- 0.08 and the observed ratio was 1.14 +/- 0.12 (n = 15; mean +/- S.E. of mean). The difference in these means was not significant (P greater than 0.20). The mean predicted Cl- flux ratio was 11.4 +/- 0.9 and the mean observed ratio was 1.38 +/- 0.27 (n = 10). The difference in these means was significant (P less than 0.001). 3. Ouabain, at 10(-6) M in the serosal solution, produced a significant (P less than 0.01) reduction in the Na+ efflux while having no significant (P greater than 0.40) effect on the Na+ influx. The agreement between the predicted (1.70 +/- 0.14) and observed (1.72 +/- 0.18) Na+ flux ratios after ouabain treatment suggested that this effect could be completely attributed to the depolarization of the epithelium secondary to ATPase inhibition. 4. beta-adrenergic activation by isoprenaline stimulated the Cl- efflux 24.2% and alpha-adrenergic activation by noradrenaline inhibited the Cl- efflux 66.5%. These changes occurred oppositely to those predicted by the changes in the electrical gradient produced by these agents, while the changes in the Cl- influxes corresponded to the electrical changes. Short-circuit experiments confirmed these effects on the Cl- efflux and the lack of effects on the Cl- influx. 5. The results suggested that Na+ was near theromodynamic equilibrium and that the unidirectional fluxes were passive. The effects of alpha- and beta-adrenergic activation suggested that the active Cl- secretion may be antagonistically regulated by catecholamines.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005260:Female; D005399:Fishes / Q000378:metabolism*; D005880:Gills / Q000378:metabolism*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D002712:Chlorides; D010042:Ouabain; D012964:Sodium; D007545:Isoproterenol; D009638:Norepinephrine