King B W, Bose D
Circ Res. 1983 Jan;52(1):65-75. doi: 10.1161/01.res.52.1.65.
Biphasic contractions were produced in dog trabeculae by replacing 90-95% of the calcium in the bathing solution with strontium. These conditions produced prolonged action potentials accompanied by contractions with two distinct phasic components. The early component disappeared slowly when the remaining Ca++ was removed, whereas the late component was eliminated quickly when Sr++ was removed. Manganese ion (0.25 mM) preferentially decreased the late component without changing the action potential, whereas caffeine and ryanodine decreased or eliminated the early component. Ryanodine did not alter the action potential. Isoproterenol rapidly increased the early component and, more slowly and to a lesser degree, increased the late component. The results suggest that the early component is caused by intracellular release of activator cation, probably from the sarcoplasmic reticulum, whereas the late component is the result of Sr++ entry across the sarcolemma, possibly by way of the slow inward current.
通过用锶替代浴液中90 - 95%的钙，在犬小梁肌中产生双相收缩。这些条件产生了延长的动作电位，并伴有具有两个不同相成分的收缩。当去除剩余的Ca++时，早期成分缓慢消失，而当去除Sr++时，晚期成分迅速消除。锰离子（0.25 mM）优先降低晚期成分而不改变动作电位，而咖啡因和兰尼碱降低或消除早期成分。兰尼碱不改变动作电位。异丙肾上腺素迅速增加早期成分，并且更缓慢且程度较小地增加晚期成分。结果表明，早期成分是由激活阳离子的细胞内释放引起的，可能来自肌浆网，而晚期成分是Sr++跨肌膜进入的结果，可能是通过缓慢内向电流。
