title: Effects of ryanodine on the contractile force of potassium-depolarized hearts.
abstract: The relationship between cellular calcium movements and contractility was indirectly assessed in Langendorff-preparations of guinea pig hearts perfused with either Krebs-Henseleit solution or a high-potassium (22 mM) solution containing 2.4 X 10(-8) M isoproterenol. The addition of either D600 (2.4-24.0 X 10(-8) M) or ryanodine (0.24-24.0 X 10(-6) M) to hearts perfused with Krebs-Hanseleit solution produced a concentration-dependent reduction in contractile force. In potassium-depolarized, isoproterenol-restored hearts, the negative inotropic action of D600 exhibited concentration-and time-dependent changes similar to those observed in Krebs-Hanseleit solution. In contrast, addition of 0.24-75.0 X 10(6) M ryanodine to potassium-depolarized, isoproterenol-restored hearts produce a time-dependent reduction in tension followed by a concentration-dependent rebound in contractile force. These results have been interpreted to be a consequence of the respective actions of D600 and ryanodine on Ca2+ influx and on intracellular calcium stores.
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D005711:Gallopamil / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D012433:Ryanodine / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000470:Alkaloids; D012433:Ryanodine; D005711:Gallopamil; D007545:Isoproterenol; D011188:Potassium