Zarzyńska Joanna, Gajewska Małgorzata, Motyl Tomasz
Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw Agricultural University, Nowoursynowska 159, 02-787 Warsaw, Poland.
J Dairy Res. 2005 Feb;72(1):39-48. doi: 10.1017/s0022029904000639.
The decline of mammary epithelial cell (MEC) number during mammary gland involution in the cow is due to inhibition of proliferation and induction of apoptosis. Transforming growth factor-beta 1 (TGF-beta1) belongs to a group of intramammary auto/paracrine inhibitors of bovine MEC growth and inducers of apoptosis. However, the mechanism responsible for the regulation of TGF-beta1 expression in MEC is not known. The present study examined the effect of the hormones, growth hormone (GH), somatostatin (STS), 17-beta oestradiol (E2), progesterone (P4), as well as the growth factors, insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF), on TGF-beta1 expression in the bovine MEC lines, BME-UV1 and MAC-T. The model of apoptosis in bovine mammary gland in vitro was applied by reduction of fetal bovine serum (FBS) (from 10% to 2% or 0.5% FBS) in the cell environment to show the relationship between TGF-beta1 expression and apoptosis in bovine MEC. RT-PCR, Western blot and laser scanning cytometry (LSC) were used for analysis of TGF-beta1 transcript and protein level as well as apoptosis and cell cycle in examined MEC. In this model of apoptosis, FBS deficiency (mimicking the naturally occurring decline in the access of bioactive compounds and nutrients at the end of lactation and dry period) was associated with increased TGF-beta1 expression at the level of transcript and protein, induction of apoptosis and inhibition of cell cycle. Exogenous TGF-beta1, IGF-I, EGF and GH inhibited FBS-deficiency-stimulated TGF-beta1 expression. The suppressive effect of GH was reversed when cells were maintained longer in FBS-deficient medium. In general, STS, E2 and P4 increased TGF-beta1 expression. However, this effect was dependent on hormone concentration and cell line. BME-UV1 cells were much more responsive to the peptides, GH, STS, IGF-I and EGF, whereas MAC-T cells were more responsive to the steroid sex hormones: E2 and P4.
奶牛乳腺退化过程中乳腺上皮细胞（MEC）数量的减少是由于增殖受到抑制以及细胞凋亡被诱导。转化生长因子-β1（TGF-β1）属于一组乳腺内牛MEC生长的自分泌/旁分泌抑制剂和细胞凋亡诱导剂。然而，MEC中TGF-β1表达调控的机制尚不清楚。本研究检测了激素（生长激素（GH）、生长抑素（STS）、17-β雌二醇（E2）、孕酮（P4））以及生长因子（胰岛素样生长因子I（IGF-I）和表皮生长因子（EGF））对牛MEC系BME-UV1和MAC-T中TGF-β1表达的影响。通过在细胞环境中降低胎牛血清（FBS）（从10%降至2%或0.5% FBS）来应用牛乳腺体外细胞凋亡模型，以显示TGF-β1表达与牛MEC细胞凋亡之间的关系。采用逆转录聚合酶链反应（RT-PCR）、蛋白质印迹法和激光扫描细胞术（LSC）分析所检测MEC中TGF-β1转录本和蛋白水平以及细胞凋亡和细胞周期。在这个细胞凋亡模型中，FBS缺乏（模拟泌乳末期和干奶期生物活性化合物和营养物质供应自然减少的情况）与转录本和蛋白水平上TGF-β1表达增加、细胞凋亡诱导以及细胞周期抑制有关。外源性TGF-β1、IGF-I、EGF和GH抑制FBS缺乏刺激的TGF-β1表达。当细胞在FBS缺乏的培养基中培养更长时间时，GH的抑制作用被逆转。总体而言，STS、E2和P4增加TGF-β1表达。然而，这种作用取决于激素浓度和细胞系。BME-UV1细胞对肽类（GH、STS、IGF-I和EGF）反应更敏感，而MAC-T细胞对类固醇性激素（E2和P4）反应更敏感。
