Thompson L V, Balog E M, Fitts R H
Biology Department, Marquette University, Milwaukee, Wisconsin 53233.
Am J Physiol. 1992 Jun;262(6 Pt 1):C1507-12. doi: 10.1152/ajpcell.1992.262.6.C1507.
The purpose of this study was to utilize glass microelectrodes to characterize the intracellular pH (pHi) before and during recovery from fatigue in the frog semitendinosus (ST) muscle. A second objective was to evaluate the relationship between pHi and contractile function. The frog ST muscle (22 degrees C) was fatigued by direct electrical stimulation with 100-ms 150-Hz trains at 1/s for 5 min. Peak tetanic force (Po) was reduced to 8.5% of initial force and recovered in a biphasic manner, returning to the resting value by 40 min. Resting pHi was 7.00 +/- 0.02 (n = 37) and declined with fatigue to an average value of 6.42 at 3 min of recovery. During recovery pHi significantly increased and by 25 min had returned to the prefatigue value. The pHi recovery was highly correlated to the slow phase of Po recovery (r = 0.98, P less than 0.001). The mean resting membrane potential was -78 +/- 1.0 mV (n = 42) and at 3 min of recovery was depolarized to -67 +/- 4 mV. Both the peak rate of twitch force development (+dP/dt) (r = 0.99, P less than 0.001) and decline (-dP/dt) (r = 0.94, P less than 0.014) were highly correlated to pHi during the slow phase of recovery. Contraction time (CT) and one-half relaxation time (1/2RT) increased significantly and recovered exponentially. The recovery of CT and 1/2RT were both significantly correlated to pHi (r = -0.93, P less than 0.001 and r = -0.86, P less than 0.001 for CT and 1/2RT, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
本研究的目的是利用玻璃微电极来表征青蛙半腱肌（ST）疲劳恢复前及恢复过程中的细胞内pH值（pHi）。第二个目的是评估pHi与收缩功能之间的关系。将青蛙的ST肌肉（22摄氏度）以1次/秒的频率给予100毫秒、150赫兹的强直刺激持续5分钟使其疲劳。强直收缩峰值力（Po）降至初始力的8.5%，并以双相方式恢复，40分钟时恢复到静息值。静息pHi为7.00±0.02（n = 37），随着疲劳而下降，在恢复3分钟时平均降至6.42。恢复过程中pHi显著升高，25分钟时恢复到疲劳前的值。pHi的恢复与Po恢复的慢相高度相关（r = 0.98，P<0.001）。平均静息膜电位为-78±1.0毫伏（n = 42），恢复3分钟时去极化至-67±4毫伏。在恢复的慢相期间，收缩力发展的峰值速率（+dP/dt）（r = 0.99，P<0.001）和下降速率（-dP/dt）（r = 0.94，P<0.014）均与pHi高度相关。收缩时间（CT）和半松弛时间（1/2RT）显著增加并呈指数恢复。CT和1/2RT的恢复均与pHi显著相关（CT和1/2RT的r分别为-0.93，P<0.001和r = -0.86，P<0.001）。（摘要截断于250字）
