Ottaway C A, Bernaerts C, Chan B, Greenberg G R
Can J Physiol Pharmacol. 1983 Jul;61(7):664-71. doi: 10.1139/y83-103.
The interaction of the neuropeptide vasoactive intestinal peptide with human circulating mononuclear cells has been studied. Mononuclear cells were able to bind radiolabelled vasoactive intestinal peptide; the binding was rapid, reversible, saturable, and specific for vasoactive intestinal peptide. A fragment of vasoactive intestinal peptide (10-28) was 25-fold less effective than intact peptide as a competitor for the binding of the tracer. Secretin was 100-fold less effective as a competitor and glucagon competed poorly even at concentrations 10 000 times greater than that of the tracer molecule. In tracer dilution studies, the binding suggested a single class of binding sites with an apparent dissociation constant (Kd) of 2.4 X 10(-10) M and a capacity of 2 000 sites per cell. In the presence of vasoactive intestinal peptide, there was a dose-dependent augmentation of cyclic AMP in the mononuclear cells. The concentration of vasoactive intestinal peptide which produced a half-maximal effect was the same as the Kd for the peptide binding. We conclude that mononuclear cells have specific high-affinity binding sites for vasoactive intestinal peptide. Interactions between mononuclear cells and vasoactive intestinal peptide may be an important mechanism modulating local immune responses within tissues innervated by vasoactive intestinal peptide containing neurons.
已对神经肽血管活性肠肽与人循环单核细胞之间的相互作用进行了研究。单核细胞能够结合放射性标记的血管活性肠肽；这种结合迅速、可逆、可饱和，且对血管活性肠肽具有特异性。血管活性肠肽片段（10 - 28）作为示踪剂结合的竞争剂，其效力比完整肽低25倍。促胰液素作为竞争剂的效力低100倍，即使在浓度比示踪剂分子高10000倍的情况下，胰高血糖素的竞争能力也很差。在示踪剂稀释研究中，结合表明存在一类单一的结合位点，其表观解离常数（Kd）为2.4×10⁻¹⁰ M，每个细胞的结合容量为2000个位点。在血管活性肠肽存在的情况下，单核细胞中的环磷酸腺苷（cAMP）呈剂量依赖性增加。产生半数最大效应的血管活性肠肽浓度与该肽结合的Kd相同。我们得出结论，单核细胞具有血管活性肠肽的特异性高亲和力结合位点。单核细胞与血管活性肠肽之间的相互作用可能是调节由含血管活性肠肽神经元支配的组织内局部免疫反应的重要机制。
