Einwächter H M, Brommundt G
Pflugers Arch. 1978 Jun 21;375(1):69-73. doi: 10.1007/BF00584150.
Frog atrial muscle strips were placed in a double sucrose gap chamber and perfusion of the central node was arranged as to allow rapid changes of external Ca or Na concentration during long-lasting (15 s) depolarizing clamps. When the superfusing fluid was suddenly switched, the intercellular space inside the fibre bundle equilibrated with a time constant in the order of 1 s. A fast change of perfusate during clamp was followed by a delayed change of tonic (sustained) contraction. When [Ca]0 was increased from 0.25 to 4 mM, tension rose in a sigmoid manner and the level reached at the end of the clamp was almost identical with the steady control in 4 mM-Ca-Ringer. A similar tension increase occurred upon a reduction of [Na]0 from 100 to 25% of normal. At a given depolarization time course and height of the tension responses followed the ratio of [Ca]0/[Na]20. Transient tension responses are interpreted in terms of a sudden perturbation of a transmembrane Ca-Na exchange system leading to a depression of Ca pumping activity.
将蛙心房肌条置于双蔗糖间隙室中，并安排对中央节段进行灌注，以便在长时间（15秒）去极化钳制期间快速改变细胞外钙或钠浓度。当突然切换灌流液时，纤维束内的细胞间隙以约1秒的时间常数达到平衡。钳制期间灌流液的快速变化之后是强直（持续）收缩的延迟变化。当[Ca]0从0.25 mM增加到4 mM时，张力呈S形上升，钳制结束时达到的水平与在4 mM钙林格液中的稳定对照几乎相同。当[Na]0从正常的100%降低到25%时，也会出现类似的张力增加。在给定的去极化时间进程下，张力反应的高度遵循[Ca]0/[Na]20的比值。瞬时张力反应被解释为跨膜钙-钠交换系统的突然扰动导致钙泵活性降低。
