title: The branchial chloride pump in the goldfish Carassius auratus: relationship between Cl-/HCO3- and Cl-/Cl-- exchanges and the effect of thiocyanate.
abstract: 1. The effect of thiocyanate on chloride and sodium fluxes across the gill was studied in the goldfish Carassius auratus. At low external chloride concentrations, addition of SCN- to the bathing solution markedly inhibited chloride influx and efflux, the net flux being reversed, SCN- injection was without effect. SCN- had no effect on sodium fluxes when injected or added to the external medium. 2. The inhibition of chloride influx by SCN- was of a mixed type involving simultaneous modifications of the affinity constant of the carrier for Cl- and of the maximal Cl- influx. The affinity constant of the carrier for SCN- was 10 times lower than that for Cl-. 3. The gill of the goldfish was found to be practically impermeable to SCN-. 4. In the presence of external SCN-, the Cl-/HCO3- exchange was reversed: Cl- was lost against HCO3- which is absorbed. This suggests an obligatory exchange. 5. Exchange diffusion for chloride was also demonstrated. 6. A kinetic model is proposed to explain chloride and bicarbonate transport across the gill of Carassius auratus.
mesh_terms: D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism; D003530:Cyprinidae / Q000378:metabolism*; D003864:Depression, Chemical; D005880:Gills / Q000378:metabolism*; D006054:Goldfish / Q000378:metabolism*; D008954:Models, Biological; D012964:Sodium / Q000378:metabolism; D013861:Thiocyanates / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001639:Bicarbonates; D002712:Chlorides; D013861:Thiocyanates; D012964:Sodium