Developmental expression changes of insulin-like growth factors (IGFs) system genes in longissimus dorsi muscle of two pig breeds
猪背最长肌中胰岛素样生长因子(IGFs)系统基因的发育表达模式

Real-time fluorescence quantitative PCR was applied to investigate the developmental expression patterns of insulin like growth factor-1 and -2 (IGF-1 and -2), insulin like growth factor receptor -1 and -2 (IGF-1R and -2R), insulin like growth factor binding protein-3 and -5 (IGFBP-3 and -5) genes at the age of birth (0), 1, 2, 3, 4, and 5 months in long-issimus dorsi muscle of Landrace and Meishan pigs. The expression level of IGF-1 exhibited up-regulation, in contrast, the expression level of IGF-2 showed down-regulation after birth in the two pig breeds. These findings are consistent with the previous knowledge that IGF-2 is mainly expressed during the embryonic phase, IGF-1 is mainly expressed during the postnatal period, which could promote cell proliferation and ontogenesis. The expression patterns of IGFRs and IGFs were dissimilar from 0 to 5 months in the two pig breeds, which suggest that the expression changes of IGFRs may not be sub-jected to the regulation by local secretion of IGFs. Strikingly, at the age of 2 months, the expression levels of IGF-1R, IGF-2R, and IGFBP-3 reached their maximum peak values in Landrace pigs, which suggest that the 2 months after birth may be the most important growth stage for genes of insulin-like growth factors (IGFs) system to exert their biological functions from birth to 5 months. These results indicate that the mRNAs of IGFs system genes exhibit specific develop-mental expression changes between Landrace and Meishan pigs, and provides some data for further study on the mutual regulation mechanism of genes in IGFs system.