Repolarization currents in embryonic chick atrial heart cell aggregates.
Outward membrane currents in aggregates of atrial cells prepared from 7-12-d-old chick embryonic hearts were measured with the two microelectrode voltage-clamp technique. Two outward current components, Ix1 and Ix2, were found in the plateau potential range of the action potential. The Ix1 component is activated between -50 and -20 mV; the Ix2 component is activated between -15 and +20 mV. The Ix1 component inwardly rectifies, whereas Ix2 has an approximately linear current-voltage relation. These preparations lack a time-dependent pacemaker current component, even though they beat spontaneously with an interbeat interval of approximately 1 s. A mathematical model of electrical activity is described based on our measurements of time-dependent outward current, and measurements in the literature of inward current components.
D000818:Animals; D016275:Atrial Function; D002449:Cell Aggregation; D002478:Cells, Cultured; D002642:Chick Embryo; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000166:cytology; D008433:Mathematics; D008564:Membrane Potentials; D008954:Models, Biological; D009206:Myocardium / Q000166:cytology