Voltage dependence of force- and slow inward current restitution in ventricular muscle.

摘要: This study was aimed to assess the relationship among voltage-dependent processes underlying excitation-contraction coupling, viz. force restitution (FR), transmembrane Ca fluxes and release. The experiments (n=22) were performed on voltage-clamped dog trabeculae in which slow inward current measured. Standard steady-state achieved by clamp driving at 0.5 Hz, 300 ms, 70 mV depolarizing pulses from holding=resting potential 30°C. Voltage duration of single intervals between varied according five protocols. voltage dependence release tested varying equal steady-state, i.e., availability. Contractions could be elicited absence ICa (20–30 step) presence disproportionately small (above 80 mV). availability for constant test following either a variable conditioning pulse or period rest voltage. After low and, hence, depressed absent ICa, contraction is diminished normal even augmented Isi any interval (i.e., FR depressed). Diminished influx thus reduces subsequent beat. During prolonged depolarization (by 60 more) tonic response appears, but phasic cannot (FR inhibited). Upon repolarization starts zero significantly enhanced. It concluded that, during depolarization, channels are an open state, allowing free recirculation Ca, no build-up sufficient gradient site.