Vadászová-Soukup A, Soukup T
Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic.
Physiol Res. 2007;56(6):833-836. doi: 10.33549/physiolres.931349.
We have analyzed the influence of altered thyroid hormone levels on changes of MyHC protein isoforms and their mRNA transcripts in the soleus muscle of 2-, 4- and 7-month-old euthyroid (EU), hypothyroid (HY) and hyperthyroid (TH) female inbred Lewis strain rats (methimazole and T3 treatment started 3 to 4 weeks after birth). We have found that the content of the dominant MyHC 1 isoform gradually increased in the EU rats and that this increase was more progressive in the HY rats at all three stages. On the other hand, in the TH rats the content of MyHC 1 isoform was the highest in the 2-month-old rats and it decreased with an increasing length of T3 treatment. The content of the minor 2a MyHC isoform followed the opposite pattern. In contrast to the protein isoforms, the MyHC mRNA transcripts remained at similar levels. Nevertheless, in general, the MyHC 1 mRNA level was decreased and MyHC 2a transcript increased in the TH rats, while the opposite changes occurred in the HY rats. Our results thus suggest that in the rat soleus muscle, both increased and decreased levels of thyroid hormones speed up the formation of an adult slow phenotype which is demonstrated by the precocious appearance of the slow MyHC 1 isoform, but opposite to the hypothyroid status, a longer T3 application promotes the expression of the faster MyHC 2a isoform.
我们分析了甲状腺激素水平改变对2个月、4个月和7个月大的甲状腺功能正常（EU）、甲状腺功能减退（HY）和甲状腺功能亢进（TH）的雌性近交系Lewis大鼠比目鱼肌中肌球蛋白重链（MyHC）蛋白亚型及其mRNA转录本变化的影响（出生后3至4周开始用甲巯咪唑和T3治疗）。我们发现，在EU大鼠中，占主导地位的MyHC 1亚型的含量逐渐增加，并且在所有三个阶段，这种增加在HY大鼠中更为显著。另一方面，在TH大鼠中，MyHC 1亚型的含量在2个月大的大鼠中最高，并且随着T3治疗时间的延长而降低。次要的2a MyHC亚型的含量则呈现相反的模式。与蛋白亚型不同，MyHC mRNA转录本水平保持相似。然而，总体而言，在TH大鼠中MyHC 1 mRNA水平降低，MyHC 2a转录本增加，而在HY大鼠中则发生相反的变化。因此，我们的结果表明，在大鼠比目鱼肌中，甲状腺激素水平的升高和降低都加速了成年慢肌表型的形成，这表现为慢肌MyHC 1亚型的早熟出现，但与甲状腺功能减退状态相反，较长时间应用T3会促进更快的MyHC 2a亚型的表达。
