Gallo Maria, Gordon Tessa, Syrotuik Daniel, Shu Yang, Tyreman Neil, MacLean Ian, Kenwell Zoltan, Putman Charles T
Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton T6G 2H9, Alberta, Canada.
Pflugers Arch. 2006 Sep;452(6):744-55. doi: 10.1007/s00424-006-0079-0. Epub 2006 May 11.
The purpose of this study was to investigate whether creatine (Cr) supplementation during 12 weeks of phasic high-frequency voluntary wheel running would result in a faster myosin heavy chain (MHC) isoform profile in the rat mixed fast-twitch plantaris and alter its corresponding isometric contractile properties. The fast-twitch extensor digitorum longus and medial gastrocnemius and slow-twitch soleus were also studied. Forty weanling Sprague-Dawley male rats were assigned to one of four groups: creatine-sedentary (Cre-Sed); creatine-voluntary running (Cre-Run); control-sedentary (Con-Sed); control-voluntary running (Con-Run). Daily running distance was similar between Cre-Run and Con-Run. Average daily Cr ingestion was also similar being 2.4+/-0.17 and 3.0+/-0.14 g/kg in Cre-Sed and Cre-Run, respectively. Total creatine (TCr) content was elevated (P<0.03) in the plantaris of Cre-Run [211.4+/-16.9 mmol/kg dry weight (dw)], compared with Con-Run (175.1+/-5.69). In the plantaris, MHCIIb was 13% greater (P<0.00001) in Cre-Run compared with Con-Run, while MHCIId/x and MHCIIa were lower in Cre-Run by 7 and 6% (P<0.0002), respectively. No differences were observed in twitch force, time-to-peak tension, half-rise time or half-fall time. Greater tetanic force production (P<0.05) in Cre-Sed compared with Con-Sed corresponded to a 12% increase in MHCIId/x (P<0.0001) and a 12% decrease in MHCIIb (P<0.0006). The fatigue index of the plantaris at 10 s (FI(10s)) was reduced only after running (Cre-Run vs Con-Run), while in all other muscles the FI(10s) was lower only in the Cre-Sed group. In conclusion, Cr supplementation had differential effects on MHC isoform content and fatigability that depended on the level of contractile activity. Cr feeding combined with running exercise resulted in a faster MHC-based phenotype in the rat plantaris but the impact on associated isometric contractile properties was minimal.
本研究的目的是调查在为期12周的阶段性高频自愿轮转跑步期间补充肌酸（Cr）是否会使大鼠混合快肌比目鱼肌的肌球蛋白重链（MHC）亚型分布更快，并改变其相应的等长收缩特性。还研究了快肌趾长伸肌、腓肠肌内侧头和慢肌比目鱼肌。40只断奶的Sprague-Dawley雄性大鼠被分为四组之一：肌酸-久坐组（Cre-Sed）；肌酸-自愿跑步组（Cre-Run）；对照-久坐组（Con-Sed）；对照-自愿跑步组（Con-Run）。Cre-Run组和Con-Run组的每日跑步距离相似。Cre-Sed组和Cre-Run组的平均每日肌酸摄入量也相似，分别为2.4±0.17和3.0±0.14 g/kg。与Con-Run组（175.1±5.69）相比，Cre-Run组比目鱼肌的总肌酸（TCr）含量升高（P<0.03）[211.4±16.9 mmol/kg干重（dw）]。在比目鱼肌中，与Con-Run组相比，Cre-Run组的MHCIIb增加了13%（P<0.00001），而Cre-Run组的MHCIId/x和MHCIIa分别降低了7%和6%（P<0.0002）。在抽搐力、峰值张力时间、上升时间一半或下降时间一半方面未观察到差异。与Con-Sed组相比，Cre-Sed组更大的强直力产生（P<0.05）对应于MHCIId/x增加12%（P<0.0001）和MHCIIb降低12%（P<0.0006）。仅在跑步后（Cre-Run组与Con-Run组）比目鱼肌的10秒疲劳指数（FI(10s)）降低，而在所有其他肌肉中，仅Cre-Sed组的FI(10s)较低。总之，补充肌酸对MHC亚型含量和疲劳性有不同影响，这取决于收缩活动水平。肌酸喂养与跑步运动相结合导致大鼠比目鱼肌中基于MHC的表型更快，但对相关等长收缩特性的影响最小。
