Effect of temperature on Ca(2+)-dependent and mechanical modulators of relaxation in mammalian myocardium.
Effect of temperature on Ca(2+)-dependent and mechanical modulators of relaxation in mammalian myocardium.
复制标题
温度对哺乳动物心肌松弛的 Ca(2) 依赖性和机械调节剂的影响。
DOI：
10.1006/jmcc.1994.1027
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发表时间：
1994
影响因子：
5
通讯作者：
Berman,MR
中科院分区：
文献类型：
--
作者：
Dobrunz,LE;Berman,MR
很早就知道温度会影响哺乳动物心肌的抽动特征；与37℃相比，24℃时的持续时间更长，作用力更大；心肌松弛也会受到温度的影响；其时间过程受各种依赖于温度的细胞内过程控制。为了研究温度对肌浆网钙处理和跨桥循环之间相互作用的影响，作为松弛时间进程的决定因素，我们观察了温度对负荷依赖性松弛(LDOR)的影响。幅度为90%、80%…的负载钳位大鼠右室乳头肌(n=7)在24℃、30℃和37℃时记录到10%的峰值等长力，并分析其松弛的负荷依赖性。温度升高使LDOR减弱，提示肌浆网的作用相对于松弛时间进程的机械决定因素而降低。因此，为了更直接地探讨[Ca~(2+)]_1瞬时和力学松弛决定因素的变化的相对贡献，我们测量了T+df/dt(到达峰值的时间+df/dt)作为[Ca~(2+)]_1峰值时间的指示器，并测量了τf(力从10%发展到最后的指数衰减的时间常数)作为力学动力学的指示器。[Ca~(2+)]_1瞬变过程和力学过程均随温度升高而加快，表现为INT+df/dt和τf：的降低，而T+df/dt/τ比值增大。我们将LDOR的降低和INT+df/dt/τ的增加解释为机械动力学比肌浆网钙离子处理对温度更敏感。
Temperature has long been known to affect mammalian cardiac muscle twitch characteristics; duration is prolonged and force is greater at 24°C compared to 37°C. Myocardial relaxation is also influenced by temperature; its time course is governed by a variety of temperature dependent intracellular processes. To investigate the effects of temperature on the interplay between sarcoplasmic reticulum calcium handling and crossbridge cycling as determinants of relaxation time course, we looked at the effects of temperature on load dependence of relaxation (LDoR). Load clamps of amplitude 90%, 80%…10% of peak developed isometric force were recorded at 24°C, 30° and 37°C in rat right ventricular papillary muscles (n=7), and load dependence of relaxation was analysed. Increasing temperature attenuated LDoR, suggesting there is a decrease in the efficacy of the sarcoplasmic reticulum relative to mechanical determinants of relaxation time course. Therefore, to more directly probe the relative contributions of changes in the [Ca2+]1transient and mechanical determinants of relaxation, we measuredT+dF/dt(time to peak +dF/dt) as an indicator of the timing of peak [Ca2+]1, and τf(the time constant of the final exponential decay of force from 10% developed force) as an indicator of mechanical kinetics. Both the [Ca2+]1transient and mechanical processes became faster with increasing temperature, as indicated by decreases inT+dF/dtand τf: however, the ratioT+dF/dt/τfincreased. We interpret the decrease in LDoR and the increase inT+dF/dt/τfas demonstrating that mechanical kinetics are more sensitive to temperature than is sarcoplasmic reticulum Ca2+handling.