外源T3对鸭胚骨骼肌发育和MyoD mRNA表达的影响

Effects of exogenous T3 on the duck embryo skeletal muscle development and expression of MyoD mRNA

甲状腺激素(thyroid hormones,THs)是体内肌肉发育的重要调节因子,MyoD在骨骼肌特异基因的转录调控,肌细胞的定向和分化中起着主要作用。为探讨三碘甲状腺原氨酸(triiodothyronine,T3)对鸭胚骨骼肌生长发育和Myod mRNA表达的影响,分别注射100μL含0.25μg(注射组)和0μg(对照组)T3的生理盐水溶液到入孵前的鸭种蛋蛋清内,检测鸭胚骨骼肌发育和MyoD mRNA的表达情况。结果表明,外源T3对鸭胚胸肌率、腿肌重和腿肌率的影响不显著(P>0.05),但显著提高27胚龄鸭胚的体重和胸肌重(P<0.05);胸肌MyoD mRNA表达与胸肌重的变化趋势相一致,其中27胚龄注射组胸肌的表达水平显著高于对照组(P<0.05);注射组腿肌MyoD mRNA表达在13胚龄显著提高(P<0.05),与腿肌发育早于胸肌相一致;注射组胸肌MyoD mRNA表达与胸肌重呈显著正线性相关,胸肌率呈负相关,腿肌MyoD mRNA与腿肌重呈负线性相关。结果显示,外源T3提高了出雏前鸭胚的体重和胸肌重,可能是通过调节MyoD mRNA表达参与胸肌的生长发育。

Thyroid hormones are major determinants of skeletal muscle development in vivo. MyoD p!ays a major role in skeletal muscle specific gene transcription and cell orientation and differentiation. In order to investigate the effect of triiodothyronine （T3） on duck embryonic skeletal muscle development and the expression of MyoD mRNA, 100 μL with 0 （control group） or 0.25 μg （injected group） T3 saline solution was injected into the duck albumen before hatching. The skeletal muscle weight and the MyoD mRNA expression level were detected at different embryonic ages. The results showed that exogenous T3 had no significant influence on breast muscle percentage, leg muscle weight and percentage （P〉0.05）, but significantly increased the body weight and breast muscle weight in the 27-embryo-age embryos （P〈0.05）. MyoD mRNA expression trend was consistent with the breast muscle weight expression level in which injected group was significantly higher than that of control group at 27-embryonic-age. MyoD mRNA expression level in leg muscle increased significantly in the 13-embryo-age embryos, which was consistent with the result that the leg muscle development was earlier than breast muscle. There was a significant positive linear correlation between MyoD mRNA expression and breast muscle weight, but showed a negative linear correlation between breast muscle percentage and leg muscle weight in the injected group. In conclusion, the results indicated that adding exogenous T3 in duck egg increased the body weight and breast muscle weight before hatching by regulating MyoD mRNA expression in breast muscle.