尾悬吊大鼠比目鱼肌肌钙蛋白I异构体的转化与睾丸萎缩

目的 确定大鼠比目鱼肌肌钙Ⅰ（TnI)发生转化的时间。并分析其与比目鱼肌萎缩时间过程间的相关关系；分析睾酮水平降低与抗重力肌萎缩速度之间的关系。方法 将雄性大鼠分为8组，悬吊时间分别为3、4、5、7、14、21、28与42d。测量雄性悬吊大鼠睾丸和比目鱼肌的湿重并计算相对重量（湿重/体重）；同时采用Western blot对悬吊大鼠比目鱼肌TnI的表达水平进行观测，将雌性大鼠分为3组，悬吊时间分别为3、4与5d，测量其比目鱼肌的湿重并计算其相对重量，结果 雄性悬吊大鼠的比目鱼肌湿重和相对重量在第4天显著降低。14d萎缩程度最明显，悬吊大鼠睾丸的湿重在第5天出现显著萎缩，相对重量在第4天发生了显著萎缩，雌性悬吊大鼠比目鱼肌的湿重与相对重量4d时没有明显变化。在第5天才显著降低。比目鱼肌TnI在悬吊14d出现由ssTnI向fsTnI的转化。结论 雄性悬吊大鼠抗重力肌（比目鱼肌）发生由ssTnI向fsTnI转化的时间为14d，这与抗重力肌发生显著萎缩的时间（4d)并不一致；提示 TnI可能不是引起模拟失重后抗重力肌萎缩的随重力的降低而发生敏感变化的蛋白，同时，雌性大鼠抗重力肌发生显著萎缩的时间是5d，提示睾酮的降低可能加速了模拟失重抗重力肌的萎缩速度。

Transition of Soleus Troponin I Isoforms and Atrophy of Testis in Tail-suspended Rats.

Objective To observe the transition time of soleus troponin I (TnI) isoforms and to elucidate the relationship between soleus TnI transition and atrophy; and to analyze the time course between testis atrophy and soleus atrophy. Method Eight groups of male rats were suspended for 3, 4, 5, 7, 14, 21, 28 and 42 d, respectively. Besides, three groups of female rats were suspended for 3, 4 and 5 d respectively. Wet and relative weights (wet weight / body weight) of testis and soleus were measured. The expression of TnI was observed by Western blot. Result The relative weight of soleus of tail suspended male rats decreased significantly after 4 d of suspension as compared with control. The degree of rats soleus atrophy in the first 14 d of suspension was greater than that after 14 d. The relative weight of testis showed the same change as that of soleus. There was no significant change in the relative weight of soleus in 4 d of tail suspended female rats. The significant decrease in the relative weight of tail suspended female rats began on the 5th day. The Western blot showed that the transition from slow skeletal TnI (ssTnI) to fast skeletal TnI (fsTnI) in the soleus occurred in 14 d of tail suspension. Conclusion The overt atrophy of tail suspended male rats occurs on the 4th day. The soleus TnI transition from ssTnI to fsTnI is on the 14th day. It is suggested that the TnI is not the sensitive protein to gravity. The overt atrophy of female tail suspended rats occurs at the 5th day. This indicated that the decrease in testosterone level may accelerate the atrophy of the soleus.