title: Importance of calcium in the inotropic effect of hyperosomotic agents, norepinephrine, paired electrical stimulation, and treppe.
abstract: The data obtained from these studies demonstrate that the inotropic effect of hyperosmolar mannitol and sucrose and of paired electrical stimulation is critically influenced by extracellular calcium concentration. The inotropic effect of norepinephrine is not prevented by maximal functional extracellular calcium concentrations. Inhibition of systolic calcium flux at the cell membrane by D600 does not prevent the inotropic effect of hyperosmolar mannitol or of paired electrical stimulation but it does prevent the inotropic effect of hyperosmolar intropic effect of treppe. Thus, intracellular calcium regulation appears to be of major importance in the inotropic effect in isolated cardiac muscle of mannitol and paired pacing while systolic calcium flux at the cell membrane appears to be of major importance in the inotropic effect of treppe.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002415:Cats; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D005110:Extracellular Space / Q000378:metabolism; D005711:Gallopamil / Q000494:pharmacology; D008353:Mannitol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D009995:Osmosis; D010210:Papillary Muscles / Q000187:drug effects; D013395:Sucrose / Q000494:pharmacology
chemical_list: D005711:Gallopamil; D008353:Mannitol; D013395:Sucrose; D002118:Calcium; D009638:Norepinephrine