Conduction between isolated rabbit Purkinje and ventricular myocytes coupled by a variable resistance.
Conduction at the Purkinje-ventricular junction (PVJ) demonstrates unidirectional block under both physiological and pathophysiological conditions. Although this block is typically attributed to multidimensional electrotonic interactions, we examined possible membrane-level contributions using single, isolated rabbit Purkinje (P) and ventricular (V) myocytes coupled by an electronic circuit. When we varied the junctional resistance (Rj) between paired V myocytes, conduction block occurred at lower Rj values during conduction from the smaller to larger myocyte (115 +/- 59 M omega) than from the larger to smaller myocyte (201 +/- 51 M omega). In Purkinje-ventricular myocyte pairs, however, block occurred at lower Rj values during P-to-V conduction (85 +/- 39 M omega) than during V-to-P conduction (912 +/- 175 M omega), although there was little difference in the mean cell size. Companion computer simulations, performed to examine how the early platea currents affected conduction, showed that P-to-V block occurred at lower Rj values when the transient outward current was increased or the calcium current was decreased in the model P cell. These results suggest that intrinsic differences in phase 1 repolarization can contribute to unidirectional block at the PVJ.
Huelsing
D J
DJ
Department of Biomedical Engineering, Tulane University, New Orleans, Louisiana 70125, USA.
Spitzer
K W
KW
Cordeiro
J M
JM
Pollard
A E
AE
D000818:Animals; D002118:Calcium / Q000502:physiology; D048429:Cell Size / Q000502:physiology; D003198:Computer Simulation; D004553:Electric Conductivity; D017097:Electric Impedance; D066298:In Vitro Techniques; D008297:Male; D008955:Models, Cardiovascular; D009206:Myocardium / Q000166:cytology; D009431:Neural Conduction / Q000502:physiology*; D011690:Purkinje Fibers / Q000502:physiology*; D011817:Rabbits; D016276:Ventricular Function / Q000502:physiology*
D002118:Calcium