Nakajima M, Yamamoto M, Ushikubi F, Okuma M, Fujiwara M, Narumiya S
Department of Pharmacology, Kyoto University Faculty of Medicine, Japan.
Biochem Biophys Res Commun. 1989 Feb 15;158(3):958-65. doi: 10.1016/0006-291x(89)92815-5.
Using [125I]I-S-145-OH, a radiolabeled derivative of a thromboxane (TX) A2 receptor antagonist, we have studied the expression of the TXA2 receptor in several lines of cultured leukemia cells. Specific binding of the ligand was observed in cells of two human erythroleukemia cell lines, K562 and HEL. However, only negligible binding was seen in HL-60 human promyelocytic leukemia cells and L-1210 murine leukemia cells. Scatchard analyses revealed a curvilinear plot which indicated the existence of two classes of binding sites in these cells. The Kd and Bmax values of the high and low affinity bindings in HEL cells were 2.4 nM and 24 fmol/10(6) cells, and 58 nM and 360 fmol/10(6) cells, respectively. These values in K562 cells were 2.8 nM and 16 fmol/10(6) cells, and 18 nM and 46 fmol/10(6) cells, respectively. The addition of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) to the cultures of K562 and HEL cells caused a concentration- and time-dependent increase in the binding activity. TPA at 10(-8) M increased the Bmax values of both high and low affinity bindings approximately 3 times without significant change in their Kd values and these increases were inhibited by the addition of actinomycin D. Both classes of the binding in cells of each cell line were specifically displaced by several TXA2/prostaglandin (PG) H2 analogues, although the relative specificities to the analogues were different in the two classes. These results suggest that both HEL and K562 cells express the TXA2 receptor on their cell surface and TPA strongly induces this expression in these cells.
利用血栓素（TX）A2受体拮抗剂的放射性标记衍生物[125I]I-S-145-OH，我们研究了几种培养的白血病细胞系中TX A2受体的表达。在两种人红白血病细胞系K562和HEL的细胞中观察到配体的特异性结合。然而，在HL-60人早幼粒细胞白血病细胞和L-1210小鼠白血病细胞中仅观察到可忽略不计的结合。Scatchard分析显示出一条曲线，表明这些细胞中存在两类结合位点。HEL细胞中高亲和力和低亲和力结合的Kd值和Bmax值分别为2.4 nM和24 fmol/10(6)个细胞，以及58 nM和360 fmol/10(6)个细胞。K562细胞中的这些值分别为2.8 nM和16 fmol/10(6)个细胞，以及18 nM和46 fmol/10(6)个细胞。向K562和HEL细胞培养物中添加12-O-十四烷酰佛波醇-13-乙酸酯（TPA）导致结合活性呈浓度和时间依赖性增加。10(-8) M的TPA使高亲和力和低亲和力结合的Bmax值增加约3倍，而其Kd值无显著变化，并且这些增加被放线菌素D的添加所抑制。每个细胞系细胞中的两类结合都被几种TX A2/前列腺素（PG）H2类似物特异性取代，尽管两类对类似物的相对特异性不同。这些结果表明，HEL和K562细胞在其细胞表面均表达TX A2受体，并且TPA强烈诱导这些细胞中的这种表达。
