高血圧ラット心筋の機械的回復曲線から求めた筋小胞体のCa含量と放出の関係

抄録

We have recently developed a method for determination of the time courses of the junctional sarcoplasmic reticulum(JSR) Ca²⁺replenishment and release in heart muscle by examining the time courses of the mechanical restitution after varying magnitudes of twitch contractions . To study Ca²⁺ handling by the JSR in the heart muscle of the hypertensive rat(SHR), we applied this method to the heart muscle of the SHR and the control(WKY).The mechanical restitution consisted of a pre-twitch latency period followed by a rapid and a subsequent much slower restitution of twitch force in both the SHR and the WKY. The rate of rapid restitution was independent of the magnitude of the preceding twitch in the WKY and the SHR, besides that it was smaller after the rested state twitch than the smaller twitch in the SHR. The rate of rapid restitution was similar in the WKY and the SHR unless the magnitude of the preceding twitch in the latter was smaller than about 1/2 of the rested state twitch. Based on this finding, the functions G(t) and H(t) , representing the time courses of the JSR Ca²⁺ replenishment and release, respectively, were derived graphically from a family of the mechanical restitution curves for the WKY and the SHR. The result suggests that the G(t) is a monotonically increasing function with time,while the H(t) a sigmoid function, and that the JSR Ca²⁺ content immediately after the rested state twitch is much smaller in the SHR than the WKY. [Jpn J Physiol 54 Suppl:S102 (2004)]