The preliminary study on the effects of growth hormone and insulin-like growth factor-I on κ-casein synthesis in bovine mammary epithelial cells in vitro

The effects of growth hormone (GH) and insulin-like growth factor-I (IGF-I) on protein synthesis and gene expression of κ-casein in bovine mammary epithelial cell in vitro were studied. The treatments were designed as follows: the growth medium without serum was set as the control group, while the treatments were medium supplemented with GH (100 ng/ml), IGF-I (100 ng/ml), and GH (100 ng/ml) + IGF-I (100 ng/ml). The quantity of κ-casein protein was measured by ELISA, and the κ-casein gene (CSN3) expression was examined by real-time quantitative PCR (RT-qPCR). Compared with the control group, all the experimental groups had greater (p < 0.05) expression of CSN3. The concentration of κ-casein followed a similar response as CSN3, but the difference between the treatments and the control was not statistically significant (p > 0.05). Furthermore, no synergistic effect of GH and IGF-I was observed for both the κ-casein concentration and CSN3 expression. It is therefore concluded that GH or IGF-I can independently promote the expression of CSN3 in bovine mammary epithelial cells in vitro.