Duhamel T A, Perco J G, Green H J
Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Am J Physiol Regul Integr Comp Physiol. 2006 Oct;291(4):R1100-10. doi: 10.1152/ajpregu.00858.2005. Epub 2006 May 11.
The hypothesis tested was that disturbances in the sarcoplasmic reticulum (SR) Ca2+-cycling responses to exercise would associate with muscle glycogen reserves. Ten untrained males [peak O2 consumption (VO2 peak) = 3.41 +/- 0.20 (SE) l/min] performed a standardized cycle test (approximately 70% VO2 peak) on two occasions, namely, following 4 days of a high (Hi CHO)- and 4 days of a low (Lo CHO)-carbohydrate diet. Both Hi CHO and Lo CHO were preceded by a session of prolonged exercise designed to deplete muscle glycogen. SR Ca2+ cycling in crude homogenates prepared from vastus lateralis samples indicated higher (P < 0.05) Ca2+ uptake (microM x g protein(-1) x min(-1)) in Hi CHO compared with Lo CHO at 30 min (2.93 +/- 0.10 vs. 2.23 +/- 0.12) and at 67 min (2.77 +/- 0.16 vs. 2.10 +/- 0.12) of exercise, the point of fatigue in Lo CHO. Similar effects (P < 0.05) were noted between conditions for maximal Ca2+-ATPase (microM x g protein(-1) x min(-1)) at 30 min (142 +/- 8.5 vs. 107 +/- 5.0) and at 67 min (130 +/- 4.5 vs. 101 +/- 4.7). Both phase 1 and phase 2 Ca2+ release were 23 and 37% higher (P < 0.05) at 30 min of exercise and 15 and 34% higher (P < 0.05), at 67 min during Hi CHO compared with Lo CHO, respectively. No differences between conditions were observed at rest for any of these SR properties. Total muscle glycogen (mmol glucosyl units/kg dry wt) was higher (P < 0.05) in Hi CHO compared with Lo CHO at rest (+36%), 30 min (+53%), and at 67 min (+44%) of cycling. These results indicate that exercise-induced reductions in SR Ca2+-cycling properties occur earlier in exercise during low glycogen states compared with high glycogen states.
所检验的假设是，肌浆网（SR）对运动的Ca2+循环反应紊乱与肌肉糖原储备有关。10名未经训练的男性[峰值耗氧量（VO2峰值）=3.41±0.20（标准误）升/分钟]在两种情况下进行了标准化的自行车测试（约为VO2峰值的70%），即分别在高碳水化合物（Hi CHO）饮食4天和低碳水化合物（Lo CHO）饮食4天后。在Hi CHO和Lo CHO饮食之前都进行了一段长时间的运动，以耗尽肌肉糖原。从股外侧肌样本制备的粗匀浆中的SR Ca2+循环表明，在运动30分钟（2.93±0.10对2.23±0.12）和67分钟（2.77±0.16对2.10±0.12，即Lo CHO组出现疲劳的时间点）时，Hi CHO组的Ca2+摄取量（微摩尔/克蛋白质-1×分钟-1）高于Lo CHO组（P<0.05）。在30分钟（142±8.5对107±5.0）和67分钟（130±4.5对101±4.7）时，两种情况下最大Ca2+-ATP酶（微摩尔/克蛋白质-1×分钟-1）也有类似的差异（P<0.05）。在运动30分钟时，Hi CHO组的第1阶段和第2阶段Ca2+释放分别比Lo CHO组高23%和37%（P<0.05），在运动67分钟时分别高15%和34%（P<0.05）。在静息状态下，这些SR特性在两种情况下均未观察到差异。在静息时、骑行30分钟时和67分钟时，Hi CHO组的总肌肉糖原（毫摩尔葡萄糖基单位/千克干重）均高于Lo CHO组（P<0.05），分别高出36%、53%和44%。这些结果表明，与高糖原状态相比，在低糖原状态下运动时，运动诱导的SR Ca2+循环特性降低出现得更早。
