D'Ambra R, Surana M, Efrat S, Starr R G, Fleischer N
Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461.
Endocrinology. 1990 Jun;126(6):2815-22. doi: 10.1210/endo-126-6-2815.
Insulin secretory physiology has been characterized in tumor cell lines derived by primary culture of insulinomas that developed in transgenic mice expressing the large T-antigen of SV40 in pancreatic islet beta-cells. Cells in one of these lines, beta TC-3, contain large amounts of insulin (3100 +/- 294 ng/100 micrograms cellular protein). Constitutive release of insulin over 2 h in static incubation was low at 31.9 ng/100 micrograms protein and was increased 2-fold by glucose (16.7 mM) and 8-fold by depolarizing concentrations of potassium (45 mM). Isobutylmethylxanthine (IBMX; 0.5 mM) and forskolin (5 and 50 microM), which elevated cellular levels of cAMP, were ineffective as secretagogues, but dramatically potentiated glucose and potassium effects on insulin release (6.5- and 4-fold, respectively). A variety of other known insulin secretagogues stimulated insulin release in a manner analogous to their effects in normal islets. The sulfonylurea glipizide (1 microM) and the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (1 microM) stimulated insulin release 3.4- and 13.7-fold, respectively. The cholinergic agonist carbachol (2 microM) was ineffective alone, but potentiated glucose-induced insulin release 2.8-fold. Comparable stimulation of insulin release by glucose (16.7 mM) and glucose (16.7 mM) plus IBMX (0.5 mM) was noted with several other beta TC lines, which were derived independently from separate transgenic mice. Glucose- and glucose- plus IBMX (0.5 mM)-induced insulin release occurred progressively from 0.15-16.7 mM, indicating that insulin release from beta TC-3 cells occurred at much lower levels than that from normal islets. However, as in the normal islet, the glucose concentration dependency for insulin release was highly correlated (r = 0.93) with the glucose concentration dependency for glucose utilization (measured by 3H2O formation from [5-3H]glucose). This suggests that glucose induces insulin release from beta TC-3 cells by a mechanism similar to that in the normal islet. The high insulin content, the multifold stimulation of insulin release by a variety of secretagogues, their convenient propagation in culture, and the renewable source of these cell lines make the beta TC cells a convenient model for studies of beta-cell function.
胰岛素分泌生理学已在源自胰岛素瘤原代培养的肿瘤细胞系中得到表征，这些胰岛素瘤是在胰岛β细胞中表达SV40大T抗原的转基因小鼠中形成的。其中一个细胞系beta TC - 3中的细胞含有大量胰岛素（3100±294 ng/100微克细胞蛋白）。在静态孵育2小时期间，胰岛素的组成性释放较低，为31.9 ng/100微克蛋白，葡萄糖（16.7 mM）可使其增加2倍，去极化浓度的钾（45 mM）可使其增加8倍。异丁基甲基黄嘌呤（IBMX；0.5 mM）和福斯可林（5和50 microM）可提高细胞内cAMP水平，但作为促分泌剂无效，但可显著增强葡萄糖和钾对胰岛素释放的作用（分别为6.5倍和4倍）。多种其他已知的胰岛素促分泌剂以与其在正常胰岛中的作用类似的方式刺激胰岛素释放。磺酰脲类格列吡嗪（1 microM）和促肿瘤佛波酯12 - O - 十四酰佛波醇 - 13 - 乙酸酯（1 microM）分别刺激胰岛素释放3.4倍和13.7倍。胆碱能激动剂卡巴胆碱（2 microM）单独无效，但可使葡萄糖诱导的胰岛素释放增加2.8倍。用其他几个独立源自不同转基因小鼠的beta TC细胞系也观察到了葡萄糖（16.7 mM）以及葡萄糖（16.7 mM）加IBMX（0.5 mM）对胰岛素释放的类似刺激。葡萄糖以及葡萄糖加IBMX（0.5 mM）诱导的胰岛素释放在0.15 - 16.7 mM范围内逐渐发生，这表明beta TC - 3细胞释放胰岛素的水平远低于正常胰岛。然而，与正常胰岛一样，胰岛素释放的葡萄糖浓度依赖性与葡萄糖利用的葡萄糖浓度依赖性（通过[5 - 3H]葡萄糖形成3H2O来测量）高度相关（r = 0.93）。这表明葡萄糖通过与正常胰岛类似的机制诱导beta TC - 3细胞释放胰岛素。高胰岛素含量、多种促分泌剂对胰岛素释放的多重刺激、它们在培养中的便捷增殖以及这些细胞系的可再生来源使得beta TC细胞成为研究β细胞功能的便捷模型。
