Jakubiec-Puka A, Ciechomska I, Mackiewicz U, Langford J, Chomontowska H
Department of Cellular Biochemistry, Nencki Institute of Experimental Biology, Warszawa, Poland.
Acta Biochim Pol. 1999;46(3):823-35.
The myosin heavy chain (MHC) was studied by biochemical methods in the slow-twitch (soleus) and two fast-twitch leg muscles of the triiodothyronine treated (hyperthyroid), thyroidectomized (hypothyroid) and euthyroid (control) rats. The changes in the contents of individual MHC isoforms(MHC-1, MHC-2A, MHC-2B and MHC-2X) were evaluated in relation to the muscle mass and the total MHC content. The MHC-1 content decreased in hyperthyreosis, while it increased in hypothyreosis in the soleus and in the fast muscles. The MHC-2A content increased in hyperthyreosis and it decreased in hypothyreosis in the soleus muscle. In the fast muscles hyperthyreosis did not affect the MHC-2A content, whereas hypothyreosis caused an increase in this MHC isoform content. The MHC-2X, present only in traces or undetected in the control soleus muscle, was synthesised in considerable amount in hyperthyreosis; in hypothyreosis the MHC-2X was not detected in the soleus. In the fast muscles the content of MHC-2X was not affected by any changes in the thyroid hormone level. The MHC-2B seemed to be not influenced by hyperthyreosis in the fast muscles, whereas the hypothyreosis caused a decrease of its content. In the soleus muscle the MHC-2B was not detected in any groups of rats. The results suggest that the amount of each of the four MHC isoforms expressed in the mature rat leg muscles is influenced by the thyroid hormone in a different way. The MHC-2A and the MHC-2X are differently regulated in the soleus and in the fast muscles; thyroid hormone seems to be necessary for expression of those isoforms in the soleus muscle.
采用生化方法，对经三碘甲状腺原氨酸处理（甲状腺功能亢进）、甲状腺切除（甲状腺功能减退）及甲状腺功能正常（对照）大鼠的慢肌（比目鱼肌）和两块快肌腿部肌肉中的肌球蛋白重链（MHC）进行了研究。评估了各个MHC亚型（MHC-1、MHC-2A、MHC-2B和MHC-2X）含量的变化与肌肉质量和总MHC含量的关系。在甲状腺功能亢进时，比目鱼肌和快肌中的MHC-1含量降低，而在甲状腺功能减退时则升高。在甲状腺功能亢进时，比目鱼肌中的MHC-2A含量增加，而在甲状腺功能减退时则降低。在快肌中，甲状腺功能亢进不影响MHC-2A含量，而甲状腺功能减退则导致该MHC亚型含量增加。MHC-2X在对照比目鱼肌中仅微量存在或未检测到，在甲状腺功能亢进时大量合成；在甲状腺功能减退时，比目鱼肌中未检测到MHC-2X。在快肌中，MHC-2X的含量不受甲状腺激素水平变化的影响。在快肌中，MHC-2B似乎不受甲状腺功能亢进的影响，而甲状腺功能减退则导致其含量降低。在比目鱼肌中，任何一组大鼠均未检测到MHC-2B。结果表明，成熟大鼠腿部肌肉中表达的四种MHC亚型的含量受甲状腺激素的影响方式不同。比目鱼肌和快肌中MHC-2A和MHC-2X的调节方式不同；甲状腺激素似乎是比目鱼肌中这些亚型表达所必需的。
