Effects of External Calcium Deprivation on Single Muscle Fibers
Effects of External Calcium Deprivation on Single Muscle Fibers
复制标题
外部缺钙对单肌纤维的影响
DOI：
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发表时间：
1967
期刊：
影响因子：
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通讯作者：
M. Giménez
中科院分区：
文献类型：
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作者：
C. Caputo;M. Giménez
外部钙的释放引起单根肌纤维的抽搐反应的突然增强。增强作用为64 ± 8%。Ca ~（++）去除后，增强作用与膜去极化同时发生。该去极化为9 ± 2 mv。Ca++去除也改变动作电位。停钙后3 min，动作电位振幅下降36 ± 3 mv，峰电位最大上升和下降率分别下降55 ± 5%和63 ± 5%。A.形状的变化P.与其他抽搐反应增强剂（如Zn++）所见的不同。在短时间暴露于无钙介质后，钾诱导的挛缩显示峰值张力增强。在这样的处理之后，将钾挛缩张力与log [K]o相关联的S形曲线向左移动。钙剥夺也增加了挛缩的松弛率。这种效应取决于钙剥夺的持续时间，并且可能与钙缺乏对膜的影响有关。钙剥夺后立即发生松弛的变化，并通过突然重新给予钙逆转。抽搐和强直反应的松弛也受到钙缺乏的影响，但不像钾挛缩那样迅速。结果表明，外部钙是不直接参与的过程中负责的张力发展，支持这一过程是由细胞内钙的易位介导的观点。然而，放松过程似乎很快受到外部钙剥夺的影响。
Deprivation of external calcium causes sudden potentiation of the twitch response of single muscle fibers. The potentiation was 64 ± 8%. Potentiation is simultaneous with membrane depolarization occurring after Ca++ removal. This depolarization amounted to 9 ± 2 mv. Ca++ removal also alters the action potential. 3 min after calcium withdrawal, action potential amplitude fell by 36 ± 3 mv; maximum rates of rise and fall of the spike decreased by 55 ± 5 and 63 ± 5% respectively. Changes in shape of the A. P. differ from those seen with other potentiators of the twitch response, such as Zn++. After short exposure to calcium-free media, potassium-induced contractures show potentiation of peak tension. The S-shaped curve relating potassium contracture tension to log [K]o shifts to the left after such treatment. Calcium deprivation also increased the rate of relaxation of the contractures. This effect depends on the duration of calcium deprivation, and is probably related to the effect of calcium lack on the membrane. The change in relaxation occurred immediately after calcium deprivation, and was reversed by sudden readmission of calcium. Relaxation of twitch and tetanus responses also were affected by Ca lack, but not as rapidly as potassium contractures. The results suggest that external calcium is not directly involved in the process responsible for tension development, supporting the view that this process is mediated by translocation of intracellular calcium. The relaxation process, however, appears to be rapidly affected by deprivation of external calcium.