Qian X, Jin L, Grande J P, Lloyd R V
Department of Laboratory Medicine and Pathology, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
Endocrinology. 1996 Jul;137(7):3051-60. doi: 10.1210/endo.137.7.8770931.
Transforming growth factor-beta (TGF beta) is a member of a family of growth factors that regulates differentiation and cellular proliferation in a wide variety of tissues, including the anterior pituitary gland. TGF beta regulates the expression of various proteins, including p27Kipl (p27), a cell cycle inhibitory protein. The cell types in normal rat anterior pituitary producing TGF beta1, one of the principal isoforms of TGF beta, and p27 were examined by in situ methods. The regulation of p27 messenger RNA (mRNA) and protein by TGF beta1 was also examined in cultured anterior pituitary cells. In situ hybridization, in situ reverse transcriptase PCR, and immunocytochemical staining for pituitary hormones showed that PRL, TSH, and gonadotroph cells all had a higher percentage of cells expressing TGF beta1 mRNA and p27 protein than did GH and ACTH cells. After treatment with 10(-9) M TGF beta1 in vitro for 3 days, there were significant decreases in p27 mRNA and protein levels (P < 0.05) in normal pituitary cells. The GH3 and GHRH-CL1 cell lines, which secrete PRL and GH, had undetectable p27 protein by immunocytochemical staining and immunoblotting, although the GH3 cell line had p27 mRNA detected by reverse transcriptase PCR. Analysis of [3H]thymidine uptake in cultured dissociated pituitary cells by double staining for hormones showed that only PRL cells had significant proliferative activity during a 3-day cell culture period. There was a biphasic effect of TGF beta1 on PRL cell proliferation, with marked inhibition by 10(-9) M and a slight stimulation by 10(-13) M. These results indicate that there is a differential distribution of both TGF beta1 and p27 in various anterior pituitary cell types and that TGF beta1 directly down-regulates p27 in cultured anterior pituitary cells.
转化生长因子-β（TGF-β）是一类生长因子家族的成员，该家族可调节多种组织（包括垂体前叶）中的细胞分化和增殖。TGF-β调节多种蛋白质的表达，包括细胞周期抑制蛋白p27Kipl（p27）。通过原位方法检测了正常大鼠垂体前叶中产生TGF-β主要异构体之一TGF-β1和p27的细胞类型。还在培养的垂体前叶细胞中检测了TGF-β1对p27信使核糖核酸（mRNA）和蛋白质的调节作用。原位杂交、原位逆转录聚合酶链反应（PCR）以及垂体激素免疫细胞化学染色显示，与生长激素（GH）细胞和促肾上腺皮质激素（ACTH）细胞相比，催乳素（PRL）、促甲状腺激素（TSH）和促性腺激素细胞中表达TGF-β1 mRNA和p27蛋白的细胞百分比更高。在体外以10⁻⁹ M TGF-β1处理3天后，正常垂体细胞中p27 mRNA和蛋白水平显著降低（P < 0.05）。分泌PRL和GH的GH3和生长激素释放激素-CL1细胞系，通过免疫细胞化学染色和免疫印迹未检测到p27蛋白，尽管通过逆转录PCR在GH3细胞系中检测到了p27 mRNA。通过激素双重染色分析培养的解离垂体细胞中[³H]胸腺嘧啶核苷摄取情况，结果显示在3天的细胞培养期内只有PRL细胞具有显著的增殖活性。TGF-β1对PRL细胞增殖有双相作用，10⁻⁹ M时显著抑制，10⁻¹³ M时轻微刺激。这些结果表明，TGF-β1和p27在各种垂体前叶细胞类型中存在差异分布，并且TGF-β1在培养的垂体前叶细胞中直接下调p27。
