title: The effect of temperature on the contractile response of cardiac muscle from two frog species, Rana temporaria and Xenopus laevis, at two different calcium concentrations-II. At pH 7.0 and pH 6.6.
abstract: 1. Mechanical parameters were recorded from paced ventricular cardiac muscle strips of two amphibian species. Rana temporaria and xenopus laevis. 2. The strips contracted at pH 6.6 and 7.0 with either 1.6 or 3.0 mM Ca2+ while the temperature was changed from 5 to 30 degree C. 3. In the hearts of R. temporaria, but not in those of X. laevis, in increased Ca2+ concentration at low pH could compensate for the effect of lowered pH. 4. It is concluded that during  high CO2 tension and/or low pH the myocardium of X. laevis was more temperature dependent, less Ca2+ dependent in the Ca2+ range examined and less sensitive to the pH and/or the CO2 tension during physiological temperature and Ca2+ concentration, than the cardiac muscle of R. temporaria.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism; D011896:Rana temporaria / Q000502:physiology*; D013696:Temperature; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D002118:Calcium