Huchet C, Léoty C
Laboratoire de Physiologie Générale, Unité de Recherche Associée Centre National de la Recherche Scientifique, 1340, Ecole Nationale Vétérinaire, Nantes, France.
Am J Physiol. 1993 May;264(5 Pt 2):R867-70. doi: 10.1152/ajpregu.1993.264.5.R867.
The properties of the contractile system at different times of the year in the ferret extensor digitorum longus (EDL), soleus and cremaster muscles were examined by using chemically skinned (Triton X-100) preparations. The results show clear differences in calcium sensitivity between these skeletal muscles. The apparent calcium threshold for activation was lower in soleus than in EDL, while calcium concentrations ([Ca2+]) required to obtain the half-maximal tension, expressed as pCa50 (-log[Ca2+]), was lower in EDL than in soleus muscle. In fact, pCa50 obtained in fast and slow fibers by fitting the experimental data points by a modified Hill equation was 5.92 +/- 0.02 (n = 9) and 6.09 +/- 0.03 (n = 11) respectively. So EDL appears to be a typical fast-twitch muscle and soleus a typical slow-twitch muscle. Adult ferret cremaster muscle was composed of two types of fibers during the quiescent period similar to EDL and soleus, and only one type that was intermediate between EDL and soleus in the breeding period, as assessed by pCa50 values. These annual modifications in calcium activation of adult ferret cremaster muscle could be related to changes in the function of these muscles and may be correlated with seasonal variations of sexual activity.
利用化学去垢剂处理（Triton X - 100）的标本，研究了雪貂的趾长伸肌（EDL）、比目鱼肌和提睾肌在一年中不同时间的收缩系统特性。结果表明，这些骨骼肌在钙敏感性方面存在明显差异。比目鱼肌的激活表观钙阈值低于趾长伸肌，而获得半最大张力所需的钙浓度（[Ca2+]），以pCa50（-log[Ca2+]）表示，趾长伸肌低于比目鱼肌。实际上，通过用修正的希尔方程拟合实验数据点，在快肌纤维和慢肌纤维中获得的pCa50分别为5.92±0.02（n = 9）和6.09±0.03（n = 11）。因此，趾长伸肌似乎是典型的快肌，比目鱼肌是典型的慢肌。成年雪貂提睾肌在静止期由类似于趾长伸肌和比目鱼肌的两种纤维组成，而在繁殖期只有一种介于趾长伸肌和比目鱼肌之间的纤维类型，这是通过pCa50值评估得出的。成年雪貂提睾肌钙激活的这些年度变化可能与这些肌肉功能的变化有关，并且可能与性活动的季节性变化相关。
