The sodium and chloride dependence of chloride secretion by the opercular epithelium.
The effects of ion substitutions on the Cl- secretion rate and tissue conductance of isolated short-circuited opercular epithelia from sea-water-adapted Fundulus heteroclitus were investigated. Serosal Na+ substitution had the same effect on the Cl- secretion rate that serosal Cl- substitution had on the active component of the Cl- efflux. This similarity indicated a 1:1 Na-Cl requirement for active Cl- secretion across this epithelium, which supports the proposal of a coupled NaCl uptake mechanism at the serosal membrane of Cl- secretory epithelia. Mucosal Na+ and Cl- substitutions appeared to inhibit completely the active Cl- secretory flux. The reductions in the tissue conductance with mucosal ion substitutions suggested that this effect can be attributed to a blocking of the apical membrane Cl- conductance. These mucosal ion effects suggested a possible direct regulatory influence of the external salinity on the Cl- secretion rate and tissue conductance, which provide alternative explanations for observations with the teleost gill epithelium.
D000818:Animals; D001692:Biological Transport; D002712:Chlorides / Q000502:physiology*; D004553:Electric Conductivity; D004848:Epithelium / Q000502:physiology; D005260:Female; D005399:Fishes / Q000502:physiology*; D005880:Gills / Q000502:physiology*; D007695:Killifishes / Q000502:physiology*; D008297:Male; D012964:Sodium / Q000502:physiology*; D014882:Water-Electrolyte Balance
D002712:Chlorides; D012964:Sodium