Boussios T, Bertles J F, Goldwasser E
Hematology-Oncology Division, St. Luke's-Roosevelt Hospital Center, New York, New York 10025.
J Biol Chem. 1989 Sep 25;264(27):16017-21.
Erythropoietin (Epo) binds specifically to receptors on the surface membrane of responsive erythroid cells. In search of ontogenic changes in Epo receptor behavior, we studied characteristics of specific binding to hamster yolk sac erythroid cells during hamster ontogeny. We detected receptors specific for Epo on these cells throughout the duration of their intravascular existence (hamster gestational days 8 through 13). These receptors are saturable at an Epo concentration of 1.2 nM in the incubation medium. Attainment of equilibrium of binding prior to hormone internalization, a requirement for receptor binding assays, was possible at 10 degrees C but not at 37 degrees C. Hence, all incubations of cells with Epo were carried out at 10 degrees C. Data on specific binding analyzed by the method of Scatchard demonstrated that yolk sac erythroid cells possess a single class of Epo receptors at each stage of gestation examined. Binding affinity and numbers of receptors per cell change as ontogeny progresses: Kd (the dissociation constant) increases, a phenomenon observed in other differentiating cell systems, whereas the number of receptors per cell peaks on gestational day 10. The variability in number of receptors per cell is consonant with up and down regulation controlled by Epo availability. We propose that the progressive increase in Kd might be best explained by ontogenic changes in cell membrane structure contiguous to the receptors themselves.
促红细胞生成素（Epo）特异性结合反应性红系细胞表面膜上的受体。为了探寻Epo受体行为的个体发生变化，我们研究了仓鼠个体发育过程中仓鼠卵黄囊红系细胞特异性结合的特征。在这些细胞血管内存在的整个时期（仓鼠妊娠第8天至第13天），我们都检测到了对Epo特异的受体。在孵育培养基中，这些受体在Epo浓度为1.2 nM时可饱和。在激素内化之前达到结合平衡是受体结合测定的一个要求，这在10℃时可行，但在37℃时不行。因此，所有细胞与Epo的孵育都在10℃下进行。用Scatchard方法分析的特异性结合数据表明，在所检测的妊娠各阶段，卵黄囊红系细胞都拥有一类Epo受体。随着个体发育的进行，结合亲和力和每个细胞的受体数量会发生变化：解离常数（Kd）增加，这一现象在其他分化细胞系统中也有观察到，而每个细胞的受体数量在妊娠第10天达到峰值。每个细胞受体数量的变化与Epo可用性控制的上调和下调一致。我们认为，Kd的逐渐增加可能最好用与受体自身相邻的细胞膜结构的个体发生变化来解释。
