Sahlin K, Edström L, Sjöholm H, Hultman E
Am J Physiol. 1981 Mar;240(3):C121-6. doi: 10.1152/ajpcell.1981.240.3.C121.
The present study was undertaken to evaluate the effect of lactic acid accumulation on peak tension and relaxation rate of the isometric twitch. Isolated extensor digitorum longus muscle from rat was stimulated electrically at a frequency of 2/s under anaerobic conditions. Comparison was made with muscles in which glycolysis was blocked with iodoacetic acid (IAA). Stimulation of unpoisoned muscles for 3 min decreased tension to 50% and increased relaxation time to 250% of the initial value. Lactate increased 15-fold, and muscle pH decreased from 7.10 to 6.76. Stimulation of IAA-poisoned muscles for 1 min decreased tension to 50% but did not increase the relaxation time. Stimulation of IAA-poisoned muscle resulted in a pronounced decrease (about 50%) of the ATP and total adenine nucleotide content in muscle, whereas only a small decrease (10-15%) occurred in unpoisoned muscle. The main findings in the present study were that tension decline in unpoisoned muscle is closely related to decrease in muscle pH and increase in ADP but not to ATP content per se and that slowing of relaxation rate is closely related to decrease in muscle pH but not to muscle content of ATP or creatine phosphate.
本研究旨在评估乳酸积累对等长收缩峰值张力和舒张速率的影响。在无氧条件下，以2次/秒的频率对大鼠分离的趾长伸肌进行电刺激。将其与用碘乙酸（IAA）阻断糖酵解的肌肉进行比较。对未中毒的肌肉刺激3分钟后，张力降至初始值的50%，舒张时间增加至初始值的250%。乳酸增加了15倍，肌肉pH值从7.10降至6.76。对IAA中毒的肌肉刺激1分钟后，张力降至50%，但舒张时间未增加。刺激IAA中毒的肌肉导致肌肉中ATP和总腺嘌呤核苷酸含量显著降低（约50%），而未中毒的肌肉中仅出现小幅降低（10 - 15%）。本研究的主要发现是，未中毒肌肉中的张力下降与肌肉pH值降低和ADP增加密切相关，而与ATP含量本身无关；舒张速率减慢与肌肉pH值降低密切相关，而与肌肉中的ATP或磷酸肌酸含量无关。
