Yamauchi H, Kasuga N
Sports Medicine Laboratory, School of Medicine, Jikei University School of Medicine, Tokyo, Japan.
Nihon Seirigaku Zasshi. 1991;53(6):197-206.
We studied the fiber types and contractile properties of the extensor digitorum longus (EDL) and soleus (SOL) muscles from young adult mice, rats and guinea pigs, and the correlation between these two parameters. Individual fibers in both muscles were classified as fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG) or slow-twitch oxidative (SO) fibers according to Peter et al., and type II B, II A, or I fibers according to Brooke & Kaiser. Contractile properties were measured in situ at 37 degrees C. The isometric twitch contraction time (CT) and one-half relaxation time (1/2 RT) tended to be shortened in proportion to the area occupied by type II fibers, and type II B fibers. However, the differences between CT and fiber types were not always uniform among the three species. The CT of the rat EDL, in spite of its higher proportion of type II B fibers about 10% was the same as that of the guinea-pig EDL. The SOL of the mouse, composed of about 50% type I (SO) fibers, had a CT about as short as that of the EDL. In the case of the classification by Peter et al., the relationship between the percentage of subgroups of fast-twitch fibers and the CT or 1/2 RT, but not the resistance to fatigue, was not obvious. The resistance to fatigue tended to be enhanced in proportion to the area occupied by FOG in the EDL and by SO (type I) in the SOL. These results suggest that the contractile properties of individual fibers identified histochemically are distinct among animal species, producing interspecies differences in fiber types along with different contractile properties. However, it may be possible to compare the difference between fiber types and CT or 1/2 RT in the classification based on the pH lability of myosin ATPase, and also the difference between fiber types and resistance to fatigue in the classification based on the oxidative enzyme.
我们研究了年轻成年小鼠、大鼠和豚鼠的趾长伸肌（EDL）和比目鱼肌（SOL）的纤维类型和收缩特性，以及这两个参数之间的相关性。根据彼得等人的方法，将两块肌肉中的单个纤维分为快肌糖酵解型（FG）、快肌氧化糖酵解型（FOG）或慢肌氧化型（SO）纤维；根据布鲁克和凯泽的方法，分为II B型、II A型或I型纤维。在37℃下原位测量收缩特性。等长收缩时间（CT）和半松弛时间（1/2 RT）往往与II型纤维和II B型纤维所占面积成比例缩短。然而，CT与纤维类型之间的差异在这三个物种中并不总是一致的。大鼠EDL的CT，尽管其II B型纤维比例较高（约10%），但与豚鼠EDL的CT相同。小鼠的SOL由约50%的I型（SO）纤维组成，其CT与EDL的CT一样短。在彼得等人的分类情况下，快肌纤维亚组百分比与CT或1/2 RT之间的关系不明显，但与抗疲劳性无关。EDL中FOG所占面积以及SOL中SO（I型）所占面积与抗疲劳性呈比例增强。这些结果表明，通过组织化学鉴定的单个纤维的收缩特性在不同动物物种中是不同的，导致纤维类型和收缩特性存在种间差异。然而，在基于肌球蛋白ATP酶pH稳定性的分类中，比较纤维类型与CT或1/2 RT之间的差异，以及在基于氧化酶的分类中，比较纤维类型与抗疲劳性之间的差异可能是可行的。
