Phillips J L, Rutledge L, Winters W D
Cancer Res. 1986 Jan;46(1):239-44.
125I-Labeled human transferrin was used to study the binding of transferrin to Colo 320 DM and Colo 205 human cell lines derived from adenocarcinomas of the colon. Although transferrin uptake was greater in both cases at 37 degrees than at 4 degrees it was found that slightly greater than two-thirds of the transferrin associated with the cells at 37 degrees was not bound to surface receptors but rather had been internalized by the cells. Subsequent analysis of true surface binding at 4 degrees by Scatchard analysis allowed determination of the number of transferrin receptors as well as association constants for the interaction. The number of transferrin receptors per cell was found to be inversely related to the cell density of the cultures from which cells were removed for study. Association constants were unaffected by cell density, with average values of 1.2 and 5.4 X 10(8) M-1 obtained for Colo 320 DM and Colo 205, respectively. Additionally, maximum theoretical numbers of receptors of 1.05 X 10(5)/cell for Colo 320 DM and 1.39 X 10(5)/cell for Colo 205 were determined. Furthermore, exposure of Colo 205 cells to three different experimental situations, i.e., 60 Hz-generated electric field only (E+, 300 mA/m2rms), magnetic field only (M+, 1.0 gauss rms), and combined electric + magnetic fields at these intensities (E+M+), altered the expression of transferrin receptors as compared to a concurrently run unexposed control population of cells (E-M-). In three separate experiments the number of transferrin receptors quantitated on both M+ and E+M+ cells was independent of cell culture density and was close to or exceeded the maximum theoretical number of receptors determined for this cell line. In contrast, E+ cells expressed fewer transferrin receptors than was predicted on the basis of cell culture density.
使用¹²⁵I标记的人转铁蛋白来研究转铁蛋白与源自结肠腺癌的Colo 320 DM和Colo 205人细胞系的结合。尽管在37℃时两种情况下转铁蛋白的摄取量均高于4℃时，但发现在37℃时与细胞相关的转铁蛋白中略超过三分之二并非与表面受体结合，而是已被细胞内化。随后通过Scatchard分析对4℃时的真实表面结合进行分析，从而确定转铁蛋白受体的数量以及相互作用的结合常数。发现每个细胞的转铁蛋白受体数量与用于研究的细胞所来自的培养物的细胞密度呈负相关。结合常数不受细胞密度影响，Colo 320 DM和Colo 205分别获得的平均值为1.2和5.4×10⁸M⁻¹。此外，确定了Colo 320 DM每个细胞的最大理论受体数为1.05×10⁵/细胞，Colo 205为1.39×10⁵/细胞。此外，将Colo 205细胞暴露于三种不同的实验条件下，即仅60 Hz产生的电场（E⁺，300 mA/m²rms）、仅磁场（M⁺，1.0高斯rms）以及这些强度的组合电场 + 磁场（E⁺M⁺），与同时运行的未暴露的对照细胞群体（E⁻M⁻）相比，改变了转铁蛋白受体的表达。在三个独立实验中，在M⁺和E⁺M⁺细胞上定量的转铁蛋白受体数量与细胞培养密度无关，并且接近或超过了为该细胞系确定的最大理论受体数。相比之下，E⁺细胞表达的转铁蛋白受体比根据细胞培养密度预测的要少。
