title: Toxin pharmacology of the ATP-induced hyperpolarization in Madin-Darby canine kidney cells.
abstract: The effects of Leiurus quinquestriatus hebraeus (LQH) venom, mamba venom, Buthus tamulus (BT) venom, purified apamin and synthetic charybdotoxin on the membrane hyperpolarization induced by extracellular ATP were examined in Madin-Darby canine kidney cells. For this we used a membrane potential probe (bisoxonol) to determine the potential variations. The relation between bisoxonal fluorescence and membrane potential was established by treating Madin-Darby canine kidney cells suspended in solutions containing various external sodium concentrations with gramicidin. Extracellular ATP induced a rapid hyperpolarization that was blocked by LQH venom and synthetic charybdotoxin. BT venom also blocked the response but at a much higher concentration than that of LQH. Mamba venom (Dendroaspis polylepis) and apamin did not modify the ATP-induced hyperpolarization. We concluded that the ATP induced hyperpolarization was due to the augmentation of the potassium conductance probably through Ca(2+)-activated K+ channels sensitive to charybdotoxin but not to mamba venom. The interaction previously described between charybdotoxin and dendrotoxin (the main toxin of mamba venom) was not observed in our case.
authors.affiliation: Département de Biologie cellulaire et moléculaire, CEN Saclay, Gif sur Yvette, France.
authors.forename: M
authors.initials: M
authors.lastname: Tauc
authors.forename: M
authors.initials: M
authors.lastname: Gastineau
authors.forename: P
authors.initials: P
authors.lastname: Poujeol
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D018999:Charybdotoxin; D004285:Dogs; D004546:Elapid Venoms / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects*; D012604:Scorpion Venoms / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence
chemical_list: D004546:Elapid Venoms; D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D001030:Apamin; D000255:Adenosine Triphosphate; D002118:Calcium