Votta B, Mong S
Department of Immunology, SmithKline & French Laboratories, King of Prussia, PA 19406-0939.
Life Sci. 1990;46(4):309-13. doi: 10.1016/0024-3205(90)90038-s.
Binding of the radiolabeled platelet-activating-factor (PAF) receptor antagonist RP52770, [( 3H]-N-(3-chlorophenyl)-3-(3-pyridinyl)-1H, 3H-pyrrolo- [1,2-c]thiazole-7-carboxamide) to receptors in human lung membranes was time- dependent, protein-dependent, reversible and saturable. The dissociation constant and maximal binding density were 14 +/- 2 nM and 2.1 +/- 0.6 pmol/mg protein, respectively. [3H]-RP52770 binding to the PAF receptor was competitively displaced by PAF and receptor antagonists. The rank order of the binding affinities were PAF greater than RP52770 (+) greater than RP52770 (-) greater than CV3988, equivalent to the PAF receptor specificities determined from functional studies. Binding of PAF to [3H]-RP52770 labeled receptors was regulated by sodium, guanylylimido- diphosphate (GppNHp) and divalent cations. In the presence of EDTA, Na+ and GppNHp, in combination, binding of PAF to the receptor was maximally shifted to the right. These results clearly demonstrate that cations and guanine nucleotide can regulate the affinity states of the PAF receptor in human lung membranes.
放射性标记的血小板活化因子（PAF）受体拮抗剂RP52770，即[(3H)-N-(3-氯苯基)-3-(3-吡啶基)-1H,3H-吡咯并[1,2-c]噻唑-7-甲酰胺]与人肺膜受体的结合是时间依赖性、蛋白质依赖性、可逆且可饱和的。解离常数和最大结合密度分别为14±2 nM和2.1±0.6 pmol/mg蛋白质。[3H]-RP52770与PAF受体的结合被PAF和受体拮抗剂竞争性取代。结合亲和力的排序为PAF＞RP52770(+)＞RP52770(-)＞CV3988，这与功能研究确定的PAF受体特异性相当。PAF与[3H]-RP52770标记受体的结合受钠、鸟苷酰亚胺二磷酸（GppNHp）和二价阳离子调节。在EDTA、Na+和GppNHp共同存在的情况下，PAF与受体的结合最大程度地向右移动。这些结果清楚地表明，阳离子和鸟嘌呤核苷酸可以调节人肺膜中PAF受体的亲和力状态。
