Anhäupl T, Liebl B, Remien J
Walther-Straub-Institut, München, FRG.
J Recept Res. 1988;8(1-4):47-57. doi: 10.3109/10799898809048977.
Saturation experiments were performed on intact human peripheral mononuclear leucocytes (MNL) and MNL membranes with (-)125Iodocyanopindolol (125ICYP) over a large concentration range (1.5-600 pmol/l). The corresponding Scatchard plots were curvilinear suggesting two saturable classes of binding sites: A high affinity binding site (Bmax1 = 1000 +/- 400 sites/cell, Kd1 = 2.1 +/- 0.9 pmol/l for intact MNL and Bmax1 = 550 +/- 190 sites/cell, Kd1 = 4.1 +/- 0.9 pmol/l for MNL membranes) and a low affinity binding site (Bmax2 = 9150 +/- 3590 binding sites/cell, Kd2 = 440 +/- 50 pmol/l for intact MNL and Bmax2 = 11560 +/- 4690 sites/cell, Kd2 = 410 +/- 70 pmol/l for MNL membranes). Dissociation of (-)125ICYP from MNL was biphasic consisting of a slow dissociating component (dissociation rate constant k-1 = (0.5 +/- 0.2) X 10(-3) min-1 for intact MNL and k-1 = (1.0 +/- 0.1) X 10(-3) min-1 for MNL membranes) and a fast dissociating component (k-2 = (80 +/- 20) X 10(-3) min-1 for intact MNL and k-2 = (60 +/- 10) X 10(-3) min-1 for MNL membranes). In dissociation experiments started after equilibration with various (-)125ICYP concentrations k-1 and k-2 were independent of the equilibrium concentration, whereas the percentual occupancy of the slow and the fast dissociating component varied and was similar to the estimated fractional occupancy of either binding site at the same (-)125ICYP concentrations in saturation experiments. The association rate constant was in the same order of magnitude for both binding sites. These results suggest two independent classes of binding sites for (-)125ICYP on MNL.
利用（-）125碘氰吲哚洛尔（125ICYP）在较大浓度范围（1.5 - 600 pmol/l）内对完整的人外周血单核白细胞（MNL）和MNL膜进行了饱和实验。相应的Scatchard图呈曲线，表明存在两类可饱和的结合位点：一个高亲和力结合位点（完整MNL的Bmax1 = 1000 ± 400个位点/细胞，Kd1 = 2.1 ± 0.9 pmol/l；MNL膜的Bmax1 = 550 ± 190个位点/细胞，Kd1 = 4.1 ± 0.9 pmol/l）和一个低亲和力结合位点（完整MNL的Bmax2 = 9150 ± 3590个结合位点/细胞，Kd2 = 440 ± 50 pmol/l；MNL膜的Bmax2 = 11560 ± 4690个位点/细胞，Kd2 = 410 ± 70 pmol/l）。（-）125ICYP从MNL的解离是双相的，由一个慢解离成分（完整MNL的解离速率常数k - 1 = (0.5 ± 0.2)×10(-3) min-1，MNL膜的k - 1 = (1.0 ± 0.1)×10(-3) min-1）和一个快解离成分（完整MNL的k - 2 = (80 ± 20)×10(-3) min-1，MNL膜的k - 2 = (60 ± 10)×10(-3) min-1）组成。在与各种（-）125ICYP浓度平衡后开始的解离实验中，k - 1和k - 2与平衡浓度无关，而慢解离成分和快解离成分的占有率会变化，且与饱和实验中相同（-）125ICYP浓度下任一结合位点的估计占有率相似。两个结合位点的缔合速率常数在同一数量级。这些结果表明MNL上存在两类独立的（-）125ICYP结合位点。
