Direct effects of growth hormone on the differentiation of bovine mammary epithelial cells.

本研究的目的是利用分离和培养的牛乳腺上皮细胞（BMEC）研究生长激素（GH）对乳腺实质的直接影响及其机制1。免疫组织化学染色和聚合酶链反应显示BMEC表达GH受体蛋白和mRNA，且mRNA的表达受乳原激素（胰岛素、催乳素和地塞米松）的刺激。采用抗α -51酪蛋白抗体ELISA法检测BMEC的酪蛋白分泌。当BMEC在涂有I型胶原的transwell插入物上培养时，GH处理4-7天后，条件培养基中的酪蛋白浓度增加。生长激素和催乳素在10-100 ng/ml剂量下引起BMEC中STATS磷酸化增加。生长激素和催乳素分别在添加后30-120 min和30-60 min显著升高。使用抗磷酸MAP激酶抗体，通过western配体印迹分析测定细胞内信号传感器MAP激酶磷酸化的变化。生长激素和催乳素在100 ng/ml的剂量下刺激BMEC中MAP激酶的磷酸化30分钟，而使用抗总MAP激酶抗体的western blot分析发现，这些处理没有改变MAP激酶蛋白的数量。综上所述，生长激素直接作用于牛乳腺上皮细胞，刺激酪蛋白的合成和分泌。JAK-STAT和MAP激酶至少部分参与生长激素的作用。

The purpose of this study was to assess the direct effect of growth hormone (GH) on mammary parenchyma using isolated and cultured bovine mammary epithelial cells (BMEC) and its mechanisms1.Immunohistochemical staining and polymerase chain reaction revealed that BMEC expressed GH receptor protein and mRNA and the mRNA expression was stimulated by lactogenic hormones (insulin, prolactin and dexamethasone).2.Casein secretion from BMEC was determined by ELISA using anti-alpha-51 casein antibody. Casein concentration in conditioned medium was increased by GH treatment for 4-7 days when BMEC was cultured on transwell inserts coated with type I collagen.3.GH as well as prolactin caused an increase in STATS phosphorylation in BMEC at a dose of 10-100 ng/ml. The increases were observed 30-120 min and 30-60 min after the addition of GH and prolactin, respectively.4.Changes in the phosphorylation of MAP kinase, an intracellular signal transducer, were determined by western ligand blot analysis using anti-phospho-MAP kinase antibody. GH and prolactin stimulated the phosphorylation of MAP kinase at a dose of 100 ng/ml for 30 min in BMEC, whereas the amount of MAP kinase protein, determined by western blot analysis using anti-total MAP kinase antibody, was not changed by these treatments.In conclusion, GH acts directly on bovine mammary epithelial cells and stimulate casein synthesis and secretion. JAK-STAT and MAP kinase are involved at least partly in the effect of GH.