[Developmental expression changes of insulin-like growth factors (IGFs) system genes in longissimus dorsi muscle of two pig breeds].

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 longissimus 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 subjected 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 developmental expression changes between Landrace and Meishan pigs, and provides some data for further study on the mutual regulation mechanism of genes in IGFs system.