Acid-base changes and excitation-contraction coupling in rabbit myocardium. II. Effects on resting membrane potential, action potential characteristics and propagation velocity.
The effects of changes in acid-base parameters on the resting membrane potential, action potential characteristics and propagation velocity were studied in isolated rabbit papillary muscles. Lowering extracellular pH from 7.4 to 6.7 in a bathing solution buffered with 10 mM histidine did not alter the resting membrane potential or action potential characteristics but casused slight reduction in propagation velocity. A parallel increase in HCO3-minus concentration (up to 47 mM)and PCO2 at a constant extracellular pH of 7.4 caused a substantial decrease in action potential duration but did not alter the resting membrane potential or propagation velocity. The decrease in action potential duration was caused by the increase in HCO3-minus concentration. Propionate (47nM) caused a shortening of the action potential which was of the same magnitude as for HCO3-minus but methylsulfate (47nM) did not have this effect. The possible influence of these changes on the inotropic state of the myocardium and the cellular mechanisms involved are discussed.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002245:Carbon Dioxide / Q000494:pharmacology; D005110:Extracellular Space; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D010210:Papillary Muscles / Q000502:physiology*; D011422:Propionates / Q000494:pharmacology; D011817:Rabbits; D013431:Sulfates / Q000494:pharmacology
D001639:Bicarbonates; D011422:Propionates; D013431:Sulfates; D002245:Carbon Dioxide