TY - JOUR
T1 - Growth hormone suppresses the expression of IGFBP-5, and promotes the IGF-I-induced phosphorylation of Akt in bovine mammary epithelial cells
AU - Sakamoto, Kazuhito
AU - Yano, Tomoki
AU - Kobayashi, Takuya
AU - Hagino, Akihiko
AU - Aso, Hisashi
AU - Obara, Yoshiaki
N1 - Funding Information:
We thank Kay-Uwe Wagner, Ph.D. and Aleata A. Triplett, M.S. (University of Nebraska, USA) for their contribution to the preparation of this manuscript. This study was supported in part by a grant-in-aid (Secure and Healthy Livestock Farming Project) from the Ministry of Agriculture, Forestry and Fisheries, Japan.
PY - 2007/5
Y1 - 2007/5
N2 - Growth hormone (GH) plays a specific role to inhibit apoptosis in the bovine mammary gland through the insulin-like growth factor (IGF)-I system, however, the mechanism of GH action is poorly understood. In this study, we show that GH dramatically inhibits the expression of IGFBP-5, and GH along with IGF-I enhanced the phosphorylation of Akt through the reduction of IGF binding protein (IGFBP)-5. To determine how GH affects Akt through IGF-I in bovine mammary epithelial cells (BMECs), we examined the phosphorylation of Akt in GH treated BMECs and found that IGF-I induced phosphorylation of Akt was significantly enhanced by the treatment with GH. We demonstrated that GH reduces mRNA and protein expression of IGFBP-5 in BMECs, but it does not affect the expression of IGFBP-3. To determine that the enhanced effect of the Akt phosphorylation by the treatment of GH is due to the inhibition of the expression of IGFBP-5, we examined the effect of IGFBP-3 and -5 on the phosphorylation of Akt through IGF-I in the GH-treated BMECs. The phosphorylation of Akt was inhibited in a dose-dependent manner when IGFBP-5 was added at varying concentrations and was also inhibited in the presence of IGFBP-3. The results of this study suggest that GH plays an important role on mammary gland involution in bovine mammary epithelial cells.
AB - Growth hormone (GH) plays a specific role to inhibit apoptosis in the bovine mammary gland through the insulin-like growth factor (IGF)-I system, however, the mechanism of GH action is poorly understood. In this study, we show that GH dramatically inhibits the expression of IGFBP-5, and GH along with IGF-I enhanced the phosphorylation of Akt through the reduction of IGF binding protein (IGFBP)-5. To determine how GH affects Akt through IGF-I in bovine mammary epithelial cells (BMECs), we examined the phosphorylation of Akt in GH treated BMECs and found that IGF-I induced phosphorylation of Akt was significantly enhanced by the treatment with GH. We demonstrated that GH reduces mRNA and protein expression of IGFBP-5 in BMECs, but it does not affect the expression of IGFBP-3. To determine that the enhanced effect of the Akt phosphorylation by the treatment of GH is due to the inhibition of the expression of IGFBP-5, we examined the effect of IGFBP-3 and -5 on the phosphorylation of Akt through IGF-I in the GH-treated BMECs. The phosphorylation of Akt was inhibited in a dose-dependent manner when IGFBP-5 was added at varying concentrations and was also inhibited in the presence of IGFBP-3. The results of this study suggest that GH plays an important role on mammary gland involution in bovine mammary epithelial cells.
KW - Akt
KW - Bovine mammary epithelial cells
KW - GH
KW - IGF-I
KW - IGFBP-5
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U2 - 10.1016/j.domaniend.2006.03.005
DO - 10.1016/j.domaniend.2006.03.005
M3 - Article
C2 - 16698222
AN - SCOPUS:33947205162
SN - 0739-7240
VL - 32
SP - 260
EP - 272
JO - Domestic Animal Endocrinology
JF - Domestic Animal Endocrinology
IS - 4
ER -