心筋の単一Caチャネルのリン酸化とCaアゴニストによる修飾

概要

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Macroscopic Ca channel currents of a single cardiac muscle are composed of numerous single Ca channel currents. The elementary current were obtained from isolated guinea pig ventricular myocytes using cell-attached patch clamp technique. In response to voltage steps, channel opening occurred singly or in bursts of closely spaced unitary current amplitude (ca. 1 pA) separated by wider shut intervals. A three-state sequential scheme (Closed-Closed-Open) fits to the activation kinetics which is voltage-dependent. At single channel the voltage-dependent inactivation is manifested by the increase of blank sweeps at depolarized holding potentials. The blank sweeps occur even at sufficiently hyperpolarized holding potentials, where current-containing sweeps and blanks appear in clusters. Adrenaline increased the channel availability, i.e. decreased the percentage of blanks by increasing the average number of consecutive current-containing sweeps. A Ca agonist BAY K 8644 increased markedly the channel open time and increased the open state probability of the channel.
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