title: Strontium induces oscillatory potentials in sheep cardiac Purkinje fibers.
abstract: The induction of strontium overload and its electromechanical manifestations, the factors influencing and the mechanism underlying Sr overload were studied in Purkinje fibers perfused in vitro. Strontium: (1) can induce an oscillatory potential (Vos) and repetitive spontaneous activity at low concentrations (1.35-2.7 mM); (2) at high concentrations (5.4-10.8 mM) less frequently causes a Vos but during recovery in Tyrode solution Vos appears as Sr overload recedes; (3) decreases the maximum diastolic potential by inducing a prolonged depolarization (Vex) which subsides slowly during an interruption of drive; (4) induces a larger Vex after procedures that increase Sr loading (fast driving rates, higher [Sr]o or longer action potentials); (5) does not induce Vos and Vex when the slow channel is blocked; (6) exaggerates Vex (but not Vos) in calcium overloaded fibers; (7) exchanges with Na since in low [Na]o the twitch amplitude increases; (8) is removed from the cell at the resting potential since after a period of quiescence the first resumed twitch decreases as a function of the preceding pause duration; (9) needs Na as charge carrier since the slope of diastolic depolarization decreases in low [Na]o. Thus, Sr causes overload even at low concentrations and induces an oscillatory potential and the prolonged depolarization Vex, whose mechanism appears to be an electrogenic Sr extrusion through Na-Sr exchange.
authors.affiliation: Department of Medicine, State University of New York, Health Science Center, Brooklyn 11203.
authors.forename: M D
authors.initials: MD
authors.lastname: Gonzalez
authors.forename: M
authors.initials: M
authors.lastname: Vassalle
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D006329:Heart Conduction System / Q000187:drug effects*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D011690:Purkinje Fibers / Q000187:drug effects*; D012756:Sheep; D012964:Sodium / Q000378:metabolism; D013324:Strontium / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D012964:Sodium; D002118:Calcium; D013324:Strontium