title: Mercury blockage of apical water channels in toad skin (Bufo marinus).
abstract: 1. Net water flow (Jw) was continuously monitored across the abdominal skin of the toad Bufo marinus by means of a volumetric, automatic technique. Jw was either averaged over periods of 2 min or taken cumulatively (10 or 30 min periods). 2. The state of high water permeability induced by vasopressin or isoprenaline was reversed (88-89% inhibition of delta Jw after 1 h) by the addition of 10(-3) M HgCl2 (or CH3ClHg) to the external bathing medium. Similarly, pre-exposure of the skins to Hg2+, totally blocked the induction of the hydrosmotic response to the same agents. By itself, Hg2+ exerted only a minor (26%) stimulation of basal Jw. 3. There was a sigmoidal dose-response relationship between the reduction of the hydrosmotic effect of vasopressin (VP) and the concentration of Hg2+ in the external medium, with a half-maximal effect at 1.2 x 10(-4) M HgCl2. 4. Total replacement of Na+ by K+, Rb+ or Cs+ in the Ringer solution, caused a VP-like, hydrosmotic effect that was reversed, or prevented, by exposure to Hg2+ in a manner indistinguishable from that previously seen with vasopressin or isoprenaline. 5. The data point to the presence of a Hg(2+)-sensitive apical water pathway in stimulated epithelia, very probably constituted by water channels similar to those reported in red blood cells, amphibian bladder and mammalian kidney tubules.
authors.affiliation: Department of Physiology, Centre Médical Universitaire, Genève, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Grosso
authors.forename: R C
authors.initials: RC
authors.lastname: De Sousa
mesh_terms: D000818:Animals; D002024:Bufo marinus / Q000378:metabolism*; D002414:Cations, Monovalent / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005089:Exocytosis / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008628:Mercury / Q000008:administration & dosage / Q000494:pharmacology*; D008954:Models, Biological; D009995:Osmosis / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D012867:Skin / Q000187:drug effects* / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology; D014867:Water / Q000378:metabolism*
chemical_list: D002414:Cations, Monovalent; D014867:Water; D014667:Vasopressins; D008628:Mercury; D007545:Isoproterenol