Altringham J D, Johnston I A
J Physiol. 1985 Nov;368:491-500. doi: 10.1113/jphysiol.1985.sp015871.
Single fast myotomal fibres and small bundles of slow fibres (from the adductor pectoralis profundus muscle) were isolated from the Antarctic teleost Notothenia neglecta. Fibres were skinned by a brief detergent treatment. The effects of phosphate on the mechanical properties and ATPase activity of fast and slow fibres were studied. 20 mM-phosphate inhibited maximum isometric tension in slow fibres by 34%, but by only 11% in fast fibres. A half-maximal response was obtained at approximately 5 mM-phosphate. These concentrations are within the range measured in muscle, and the effect is probably of physiological significance. This species is of particular interest, since there is evidence that the energy supply to the fast muscle is largely based on phosphocreatine breakdown, which would result in large changes in intracellular phosphate concentration during exercise. The maximum contraction velocity of both fast and slow fibres was not affected by 10 mM-phosphate, nor was the ATPase activity of the slow fibres during isometric contraction. The phosphate-induced depression in tension in slow fibres was associated with a proportional decrease in stiffness. The rate of force recovery after rapid, small amplitude stretches and releases was increased by phosphate, as was the rate of rise of force during stretch activation. The results are discussed with reference to the different patterns of energy supply for contraction in muscle, and an attempt is made at explaining the data in terms of changes in cross-bridge kinetics.
从南极硬骨鱼小鳞犬牙南极鱼中分离出单根快速肌节纤维和小束慢速纤维（取自胸深内收肌）。通过短暂的去污剂处理使纤维脱膜。研究了磷酸盐对快速和慢速纤维力学性能及ATP酶活性的影响。20 mM磷酸盐使慢速纤维的最大等长张力降低34%，但使快速纤维仅降低11%。在约5 mM磷酸盐时获得半数最大反应。这些浓度在肌肉中测得的范围内，其作用可能具有生理意义。该物种特别令人关注，因为有证据表明快速肌肉的能量供应很大程度上基于磷酸肌酸分解，这会导致运动过程中细胞内磷酸盐浓度发生大幅变化。10 mM磷酸盐对快速和慢速纤维的最大收缩速度均无影响，对等长收缩期间慢速纤维的ATP酶活性也无影响。磷酸盐导致的慢速纤维张力降低与刚度成比例下降相关。快速小幅度拉伸和释放后力的恢复速率以及拉伸激活期间力的上升速率均因磷酸盐而增加。结合肌肉收缩能量供应的不同模式对结果进行了讨论，并尝试根据横桥动力学变化来解释这些数据。
