Temperature dependence of active tension in mammalian (rabbit psoas) muscle fibres: effect of inorganic phosphate
Temperature dependence of active tension in mammalian (rabbit psoas) muscle fibres: effect of inorganic phosphate
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DOI：
10.1111/j.1469-7793.2001.00879.x
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发表时间：
2001-11-01
影响因子：
5.5
通讯作者：
Ranatunga, KW
中科院分区：
文献类型：
--
作者：
Coupland, ME;Puchert, E;Ranatunga, KW
1.在一定温度范围（5-30 ℃）下，在化学去皮（0.5%Brij）的兔腰肌纤维中，检查了添加的无机磷酸盐（P-i，范围3-25 mM）对主动张力的影响。进行了三种类型的实验.在一种类型的实验中，肌纤维在低温（5摄氏度）下被最大程度地激活，并且在类似于60秒的逐步加热到高温期间记录其张力变化。如在先前的研究中所发现的，张力随温度而增加，并且归一化张力-（倒数）温度关系是S形的，在8 ℃时具有半最大张力。在加入25 mM P-i的情况下，标准化曲线的半最大张力温度比对照高5 ℃。斜率差异较小.在第二种类型的实验中，在主动收缩过程中检查了大温度跃变（从5到30摄氏度）期间的张力增量。在25 mM添加的Pi的存在下（30/5 ℃张力比为6-7），加热时的活性张力的相对增加显著高于不添加Pi的对照（张力比类似于3）。在第三种类型的实验中，在5、10、20和30 ℃下检查不同水平的添加的P-i（3-25 mM）（和足以将污染的P-i降低至微摩尔水平的P-i mop）对最大Ca 2+活化张力的影响。在所有温度下，随着[P-i]的增加，张力以浓度依赖的方式降低，并且数据可以用双曲线关系拟合。在5-10 ℃下，计算的过量最大张力降低[P-i]与对照的65%相似，而在20 ℃下最大降低为40%，在30 ℃下为30%。这些实验表明，P-i在腰肌纤维中引起的主动张力降低是温度敏感的，在高温下降低变得不那么明显。通过简化的肌动球蛋白ATP酶循环定性预测了P-i诱导的张力抑制的减少，其中磷酸盐前释放、力产生步骤因温度而增强。
1. The effect of added inorganic phosphate (P-i, range 3-25 mM) on active tension was examined at a range of temperatures (5-30 degreesC) in chemically skinned (0.5% Brij) rabbit psoas muscle fibres. Three types of experiments were carried out.2. In one type of experiment, a muscle fibre was maximally activated at low temperature (5 degreesC) and its tension change was recorded during stepwise heating to high temperature in similar to 60 s. As found in previous studies, the tension increased with temperature and the normalised tension-(reciprocal) temperature relation was sigmoidal, with a half-maximal tension at 8 degreesC. In the presence of 25 mM added P-i, the temperature for half-maximal tension of the normalised curve was similar to5 degreesC higher than in the control. The difference in the slope was small.3. In a second type of experiment, the tension increment during a large temperature jump (from 5 to 30 degreesC) was examined during an active contraction. The relative increase of active tension on heating was significantly higher in the presence of 25 mM added Pi (30/5 degreesC tension ratio of 6-7) than in the control with no added P-i (tension ratio of similar to3).4. In a third type of experiment, the effect on the maximal Ca2+-activated tension of different levels of added P-i (3-25 mM) (and P-i mop adequate to reduce contaminating P-i to micromolar levels) was examined at 5, 10, 20 and 30 degreesC. The tension was depressed with increased [P-i] in a concentration-dependent manner at all temperatures, and the data could be fitted with a hyperbolic relation. The calculated maximal tension depression in excess [P-i] was similar to 65 % of the control at 5-10 degreesC, in contrast to a maximal depression of 40 % at 20 degreesC and 30 % at 30 degreesC.5. These experiments indicate that the active tension depression induced by P-i in psoas fibres is temperature sensitive, the depression becoming less marked at high temperatures. A reduced P-i-induced tension depression is qualitatively predicted by a simplified actomyosin ATPase cycle where a pre-phosphate release, force-generation step is enhanced by temperature.