Temperature sensitivity of outward current in cardiac Purkinje fibers. Evidence of electrogenicity of active transport.
1. In cardiac Purkinje fibers the temperature sensitivity of the membrane current flowing after 2 sec in response to depolarizing clamp steps was recorded. When the temperature was quickly lowered (30 sec) from 37 degrees C to 20 degrees C for a period of 2 min the outward current was markedly reduced. The effect was immediately reversed upon rewarming. The reduction in outward current on cooling was most pronounced between 30 degrees C and 20 degrees C. 2. In the range of anomalous rectification cooling to 20 degrees C shifted the i.v. relation in a negative direction by a constant amount of 20 nA. Outside this potential range (negative to -80 mV and positive to -45 mV) the slope conductance was reduced with a Q10 of about 1.3. 3. In the presence of dihydroouabain cooling did not further reduce the outward current in the potential range of anomalous rectification. However, negative to -80 mV and positive to -40 mV the slope conductance was reduced. The results support the view that part of the outward current is generated by an electrogenic sodium pump which is inhibited by cooling.
D000818:Animals; D001693:Biological Transport, Active; D006329:Heart Conduction System / Q000502:physiology*; D008564:Membrane Potentials; D010042:Ouabain / Q000031:analogs & derivatives / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011690:Purkinje Fibers / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D013696:Temperature
D010042:Ouabain; D012964:Sodium; D011188:Potassium