Molecular Medicine Section, National Heart and Lung Institute, Sir Alexander Fleming Building, Imperial College London, London, SW7 2AZ, UK.
J Muscle Res Cell Motil. 2010 Jul;31(1):35-44. doi: 10.1007/s10974-010-9198-5. Epub 2010 Jan 19.
Effects of Pi (inorganic phosphate) are relevant to the in vivo function of muscle because Pi is one of the products of ATP hydrolysis by actomyosin and by the sarcoplasmic reticulum Ca(2+) pump. We have measured the Pi sensitivity of force produced by permeabilized muscle fibres from dogfish (Scyliorhinus canicula) and rabbit. The activation conditions for dogfish fibres were crucial: fibres activated from the relaxed state at 5, 12, and 20 degrees C were sensitive to Pi, whereas fibres activated from rigor at 12 degrees C were insensitive to Pi in the range 5-25 mmol l(-1). Rabbit fibres activated from rigor were sensitive to Pi. Pi sensitivity of force produced by dogfish fibres activated from the relaxed state was greater below normal body temperature (12 degrees C for dogfish) in agreement with what is known for other species. The force-temperature relationship for dogfish fibres (intact and permeabilized fibres activated from relaxed) showed that at 12 degrees C, normal body temperature, the force was near to its maximum value.
Pi（无机磷酸盐）的作用与肌肉的体内功能有关，因为 Pi 是肌球蛋白和肌浆网 Ca(2+)泵水解 ATP 的产物之一。我们已经测量了来自狗鲨（Scyliorhinus canicula）和兔的通透性肌纤维产生的力对 Pi 的敏感性。狗鲨纤维的激活条件非常关键：在 5、12 和 20°C 时从松弛状态激活的纤维对 Pi 敏感，而在 12°C 时从僵硬状态激活的纤维在 5-25mmol l(-1)范围内对 Pi 不敏感。兔纤维从僵硬状态激活时对 Pi 敏感。从松弛状态激活的狗鲨纤维产生的力对 Pi 的敏感性在低于正常体温（狗鲨为 12°C）时更大，这与其他物种的情况一致。狗鲨纤维的力-温度关系（完整纤维和从松弛状态激活的通透性纤维）表明，在 12°C，正常体温时，力接近其最大值。
