Fujiwara Y, Mantione C R, Vavrek R J, Stewart J M, Yamamura H I
Department of Pharmacology, University of Arizona College of Medicine, Tucson 85724.
Life Sci. 1989;44(22):1645-53. doi: 10.1016/0024-3205(89)90481-5.
Specific [3H]bradykinin(BK) binding was investigated in membranes from guinea-pig brain. In kinetic experiments, specific [3H]BK binding (100 pM) reached equilibrium within 15 min at 25 degrees C (k + 1 = 1.40 nM-1min-1) and the binding was reversed by the addition of 1 microM BK (k-1 = 0.069 min-1). The presence of a high affinity BK binding site was also revealed in the guinea-pig brain by equilibrium saturation studies with a Kd value of 75 pM and a Bmax value of 4.9 +/- 0.9 fmol/mg protein. In inhibition experiments, the B2 antagonists (D-Phe7-BK and Thi5,8,D-Phe7-BK) inhibited [3H]BK binding, but not the B1 antagonist (des-Arg9[Leu8]-BK). D-Arg[Hyp3, D-Phe7]BK (B4801) showed a pseudo Hill coefficient of less than one. The KH and KL values are 1.8 and 94 nM. The regional distribution study shows the highest density of BK binding sites in the pons + medulla oblongata and the spinal cord, a moderate density in the cerebral cortex and hippocampus, and a low density in other brain regions. These data support the presence of B2 BK receptors in the guinea-pig brain and spinal cord and suggest the existence of B2 subtypes in the brain. The presence of these receptors suggests that BK acts as a neurotransmitter or a neuromodulator in these tissues.
在豚鼠脑细胞膜中研究了特异性[³H]缓激肽（BK）结合。在动力学实验中，特异性[³H]BK结合（100 pM）在25℃下15分钟内达到平衡（k + 1 = 1.40 nM⁻¹min⁻¹），加入1 μM BK可使结合逆转（k⁻¹ = 0.069 min⁻¹）。通过平衡饱和研究也揭示了豚鼠脑中存在高亲和力BK结合位点，其Kd值为75 pM，Bmax值为4.9 ± 0.9 fmol/mg蛋白质。在抑制实验中，B2拮抗剂（D - Phe7 - BK和Thi5,8,D - Phe7 - BK）抑制[³H]BK结合，但B1拮抗剂（des - Arg9[Leu8] - BK）则无此作用。D - Arg[Hyp3, D - Phe7]BK（B4801）显示伪希尔系数小于1。KH和KL值分别为1.8和94 nM。区域分布研究表明，BK结合位点密度在脑桥 + 延髓和脊髓中最高，在大脑皮层和海马体中为中等密度，在其他脑区中为低密度。这些数据支持豚鼠脑和脊髓中存在B2 BK受体，并提示脑中存在B2亚型。这些受体的存在表明BK在这些组织中作为神经递质或神经调节剂发挥作用。
