TY - JOUR
T1 - Determinants of postrepolarization refractoriness in depressed mammalian ventricular muscle
AU - Rozanski, G. J.
AU - Jalife, J.
AU - Moe, G. K.
PY - 1984
Y1 - 1984
N2 - Functional determinants of postrepolarization refractoriness were studied with microelectrodes in isolated cat dog ventricular muscle preparations mounted in a three-chambered bath. Frequency-dependent conduction delay and block were readily manifested when the central segment (1 mm) was superfused with high potassium (20-30 mM) Throde's solution. Conduction disorders were attributed to postrepolarization refractoriness involving slow recovery in the amplitude of elicited subthreshold depolarizations in depressed fibers distal to the central blocked zone. Investigations of subthreshold phenomena in homogeneously depressed tissues indicated that a relatively large local response participated in the voltage displacement induced by subthreshold depolarizing currents. The local response was blocked by tetrodotoxin (10 μg/ml) or verapamil (2 χ/ml) when resting membrane potential was near -70 or -50 mV, respectively. At either level of reduced membrane potential, gradual recovery in diastolic excitability correlated closely with time-dependent recovery of the local response, the rate of which was also proportional to the current intensity applied. Thus, postrepolarization refractriness in depressed ventricular muscle fibers is a function of the time for recovery of active subthreshold properties (the local response), as well as intensity of excitatory current input. These factors may play a role in the development of delayed conduction and reentry that occur at faster heart rates under ischemic conditions.
AB - Functional determinants of postrepolarization refractoriness were studied with microelectrodes in isolated cat dog ventricular muscle preparations mounted in a three-chambered bath. Frequency-dependent conduction delay and block were readily manifested when the central segment (1 mm) was superfused with high potassium (20-30 mM) Throde's solution. Conduction disorders were attributed to postrepolarization refractoriness involving slow recovery in the amplitude of elicited subthreshold depolarizations in depressed fibers distal to the central blocked zone. Investigations of subthreshold phenomena in homogeneously depressed tissues indicated that a relatively large local response participated in the voltage displacement induced by subthreshold depolarizing currents. The local response was blocked by tetrodotoxin (10 μg/ml) or verapamil (2 χ/ml) when resting membrane potential was near -70 or -50 mV, respectively. At either level of reduced membrane potential, gradual recovery in diastolic excitability correlated closely with time-dependent recovery of the local response, the rate of which was also proportional to the current intensity applied. Thus, postrepolarization refractriness in depressed ventricular muscle fibers is a function of the time for recovery of active subthreshold properties (the local response), as well as intensity of excitatory current input. These factors may play a role in the development of delayed conduction and reentry that occur at faster heart rates under ischemic conditions.
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U2 - 10.1161/01.RES.55.4.486
DO - 10.1161/01.RES.55.4.486
M3 - Article
C2 - 6478553
AN - SCOPUS:0021679126
VL - 55
SP - 486
EP - 496
JO - Circulation Research
JF - Circulation Research
SN - 0009-7330
IS - 4
ER -