Effects of exogenous T3 on the duck embryo skeletal muscle development and expression of MyoD mRNA
Thyroid hormones are major determinants of skeletal muscle development in vivo. MyoD plays 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(P0.05), but significantly increased the body weight and breast muscle weight in the 27-embryo-age embryos(P0.05). 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.