Laughlin M H, Schaefer M E, Sturek M
Department of Veterinary Biomedical Sciences, University of Missouri, Columbia 65211.
J Appl Physiol (1985). 1992 Oct;73(4):1441-8. doi: 10.1152/jappl.1992.73.4.1441.
The purpose of this study was to test the hypothesis that exercise training induces enhanced intracellular free Ca2+ (Cai) availability to the contractile elements of cardiac cells. Cai transients were directly measured in single isolated contracting ventricular myocytes from exercise-trained (EX) and sedentary control (SED) rats. Male Sprague-Dawley rats underwent 16 wk of progressive treadmill exercise (32 m/min, 8% grade, 1.5 h/day) (EX) or were cage confined (SED). EX rats had lower resting heart rate and elevated skeletal muscle oxidative capacity. Cai was measured with the fluorescent Cai indicator fura-2. Simultaneous video monitoring indicated that myocytes suspended in physiological salt solution were quiescent until stimulated electrically at a frequency of 0.2 Hz (12-36 V, 2-ms duration). Stimulated Cai transients, measured from changes in fura-2 fluorescence, were similar in cells from EX and SED groups. Peak shortening, time to peak shortening, velocity of shortening, contraction duration, and time to half-relaxation were also similar in cells from EX and SED rats. Ryanodine (10 microM) was applied to eliminate the contribution of Ca2+ release from sarcoplasmic reticulum to the Cai transient. Verapamil was applied to eliminate the contribution of voltage-gated Ca2+ channels to Cai transients. Cai transients were also similar in cells from EX and SED groups after these pharmacological interventions. These results suggest that treadmill training of rats does not alter Cai availability to the contractile elements in isolated ventricular myocytes.
运动训练可增强心肌细胞收缩元件的细胞内游离Ca2+（Cai）可用性。直接测量运动训练（EX）大鼠和久坐对照（SED）大鼠分离的单个收缩心室肌细胞中的Cai瞬变。雄性Sprague-Dawley大鼠进行16周的渐进式跑步机运动（32米/分钟，8%坡度，1.5小时/天）（EX）或关在笼中（SED）。EX组大鼠静息心率较低，骨骼肌氧化能力增强。用荧光Cai指示剂fura-2测量Cai。同步视频监测表明，悬浮在生理盐溶液中的心肌细胞在以0.2 Hz频率（12 - 36 V，2毫秒持续时间）进行电刺激之前处于静止状态。通过fura-2荧光变化测量的刺激Cai瞬变在EX组和SED组细胞中相似。EX组和SED组大鼠细胞的峰值缩短、达到峰值缩短的时间、缩短速度、收缩持续时间和半松弛时间也相似。应用ryanodine（10 microM）以消除肌浆网Ca2+释放对Cai瞬变的贡献。应用维拉帕米以消除电压门控Ca2+通道对Cai瞬变的贡献。在这些药物干预后，EX组和SED组细胞中的Cai瞬变也相似。这些结果表明，大鼠的跑步机训练不会改变分离心室肌细胞中收缩元件的Cai可用性。
