Anion-induced dynamic behavior of apical water channels in vasopressin-sensitive epithelia exposed to mercury.
We showed recently that, in toad skins preexposed to Hg, water permeability is high in SO4-Ringer and low in Cl-Ringer. This anion effect was further investigated in Hg-treated skins and bladders of toads (Bufo marinus) in a variety of experimental conditions, including glutaraldehyde fixation and stimulation by vasopressin (VP) or isoproterenol (IP). In fixed bladders either unstimulated or stimulated with VP, net water flow (Jw) in SO4-Ringer [Jw (SO4)] was always significantly higher than Jw in Cl [Jw (Cl)]; the same applies to fixed toad skins, either unstimulated or stimulated with IP. In unfixed isolated toad epidermis challenged with IP before Hg exposure, Jw(SO4)/Jw(Cl) >> 1 approaching the ratio Jw (maximally stimulated)/Jw (basal). Therefore, anion-induced Jw changes were present whether Hg acted on epithelial water channels exocytosed by Hg itself or by hydrosomotic agents and suggest a switching between open and closed configurations of the channel protein. This anion effect was not abolished by glutaraldehyde and might be correlated with changes in intracellular chloride.
Grosso
A
A
Department of Physiology, Centre Médical Universitaire, Geneva, Switzerland.
Jaquet
P
P
Brawand
P
P
De Sousa
R C
RC
D000818:Animals; D000838:Anions / Q000494:pharmacology; D002024:Bufo marinus; D002462:Cell Membrane / Q000378:metabolism; D004817:Epidermis / Q000187:drug effects / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008628:Mercury / Q000494:pharmacology*; D012867:Skin / Q000187:drug effects / Q000378:metabolism*; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism*; D014667:Vasopressins / Q000494:pharmacology*; D014867:Water / Q000378:metabolism*
D000838:Anions; D007473:Ion Channels; D014867:Water; D014667:Vasopressins; D008628:Mercury; D007545:Isoproterenol