title: The "small" conductance chloride channel in the luminal membrane of the rectal gland of the dogfish (Squalus acanthias).
abstract: Besides the "larger" Cl- channel, with a single channel conductance of about 45 pS, a "small" channel was observed in the luminal membrane of the dogfish rectal gland. In cell excised (inside out) patches with NaCl solution on both sides, the latter channel had a single channel conductance of 11 +/- 1 pS (n = 21), and its current-voltage relationship was linear in the voltage range +90 to -90 mV. The open state probability increased moderately with negative clamp potentials. Ionic replacement studies revealed a high selectivity of Cl- over gluconate, sulfate, and iodide, whereas bromide was permeable to some extent. Also the channel is impermeable for Na+. The Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoate did not affect this "small" conductance Cl- channel. It can be concluded that the luminal membrane of stimulated rectal gland cells possesses two types of Cl- channels, which differ markedly in their characteristics.
mesh_terms: D000818:Animals; D002712:Chlorides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004284:Dogfish / Q000378:metabolism*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000145:classification* / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012491:Salt Gland / Q000378:metabolism*; D012754:Sharks / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism
chemical_list: D002712:Chlorides; D007473:Ion Channels; D000644:Quaternary Ammonium Compounds; D012964:Sodium; C027917:tetramethylammonium; D011188:Potassium