title: Mechanism of active chloride secretion by shark rectal gland: role of Na-K-ATPase in chloride transport.
abstract: The isolated rectal gland of Squalus acanthias was stimulated to secrete chloride against an electrical and a chemical gradient when perfused in vitro by theophylline and/or dibutyryl cyclic AMP. Chloride secretion was depressed by ouabain which inhibits Na-K-ATPase. Thiocyanate and furosemide also inhibited chloride secretion but ethoxzolamide, a carbonic anhydrase inhibitor, did not. Chloride transport was highly dependent on sodium concentration in the perfusate. The intracellular concentration of chloride averaged 70-80 meq/liter in intact glands, exceeding the level expected at electrochemical equilibrium and suggesting active transport of chloride into the cell. These features suggest a tentative hypothesis for chloride secretion by the rectal gland in which the uphill transport of chloride into the cytoplasm is coupled through a membrane carrier to the downhill movement of sodium along its electrochemical gradient. The latter is maintained by the Na-K-ATPase pump while chloride is extruded into the duct by electrical forces.
mesh_terms: D000251:Adenosine Triphosphatases / Q000502:physiology*; D000818:Animals; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism*; D004284:Dogfish / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012491:Salt Gland / Q000378:metabolism*; D012754:Sharks / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
chemical_list: D002712:Chlorides; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D011188:Potassium