Widman L E, Chasin L A
J Cell Physiol. 1982 Sep;112(3):316-26. doi: 10.1002/jcp.1041120303.
A subclone of the FU5-5 rat hepatoma cell line has been isolated which is inducible more than several hundred fold for the 20,000 dalton form of the major rat urinary protein alpha 2u-globulin. The basal relative synthetic rate (RSR) in growth medium containing 10% fetal calf serum was less than 2 X 10(-6) of total protein synthesis. Both dexamethasone and insulin were necessary for induction, and yielded a maximum induced RSR of 4-8 X 10(-3). Triiodothyronine (T3), dihydrotestosterone (DHT), rat growth hormone (GH), and estrogen, all of which have been shown to influence the induction of alpha 2u-globulin in the intact rat, were without effect on the cell line. A factor present in fetal calf serum was also necessary for maximum induction, since dexamethasone plus insulin in serum-free medium raised the RSR to only 3 X 10(-5); exogenous T3, GH, and DHT could not substitute for this serum factor. The kinetics of induction by dexamethasone were slow, with a lag of approximately 48 hr followed by a period of increasing RSR for 6-20 days. Removal of dexamethasone from induced cells led to an exponential decline in the RSR (t 1/2 15 hr). The concentrations of dexamethasone and insulin that could yield half maximum induction were 5 X 10(-8)M and 3 X 10(-11)M, respectively. Higher concentrations of insulin, although still in physiological range (10(-9)M), inhibited induction. At yet higher insulin levels, beyond the physiological range, alpha 2u-globulin synthesis returned to maximum values. The lack of DHT, T3, and GH requirement for alpha 2u-globulin induction in this cell line may mean that a regulatory aberrancy has occurred in this transformed cell line, or, alternatively, that these hormones act indirectly in the intact animal. This cell line should prove useful for the study of the molecular events associated with alpha 2u-globulin induction and for genetic approaches to the problem of multihormonal regulation of gene expression.
已分离出FU5-5大鼠肝癌细胞系的一个亚克隆，该亚克隆对大鼠主要尿蛋白α2u-球蛋白的20,000道尔顿形式的诱导倍数可达数百倍以上。在含10%胎牛血清的生长培养基中，基础相对合成率（RSR）低于总蛋白合成的2×10⁻⁶。地塞米松和胰岛素对诱导均是必需的，诱导后的最大RSR为4 - 8×10⁻³。三碘甲状腺原氨酸（T3）、二氢睾酮（DHT）、大鼠生长激素（GH）和雌激素，所有这些在完整大鼠中均已显示会影响α2u-球蛋白的诱导，但对该细胞系均无作用。胎牛血清中存在的一种因子对最大诱导也是必需的，因为在无血清培养基中地塞米松加胰岛素只能将RSR提高到3×10⁻⁵；外源性T3、GH和DHT不能替代这种血清因子。地塞米松诱导的动力学较慢，有大约48小时的滞后，随后是RSR增加6 - 20天的时期。从诱导细胞中去除地塞米松会导致RSR呈指数下降（半衰期15小时）。产生半数最大诱导的地塞米松和胰岛素浓度分别为5×10⁻⁸M和3×10⁻¹¹M。更高浓度的胰岛素，尽管仍在生理范围内（10⁻⁹M），但会抑制诱导。在更高的胰岛素水平，超出生理范围时，α2u-球蛋白合成恢复到最大值。该细胞系对α2u-球蛋白诱导相关分子事件的研究以及对基因表达多激素调节问题的遗传学方法研究应是有用的。
