Segond von Banchet G, Petersen M, Heppelmann B
Physiologisches Institut, Universität Würzburg, Germany.
Neuroscience. 1996 Dec;75(4):1211-8. doi: 10.1016/0306-4522(96)00346-6.
The endogenous nonapeptide bradykinin is a powerful substance which activates nociceptors, resulting in the sensation of pain in man. We used a newly developed non-radioactive method to detect bradykinin binding sites in isolated dorsal root ganglion cells with gold-labelled bradykinin. In a subpopulation of cells, gold-labelled bradykinin was bound in different quantities. The proportion of somata with bradykinin binding markedly depended on the length of time in culture. After 0.75 days, bradykinin was bound to 43% of somata. This proportion increased to 85% after 1.75 days and then decreased to 27% after 5.75 days. Bradykinin was bound to cells of all sizes, ranging from 40 to 2000 microns2 with a maximum of 200-300 microns2. In some cells, binding was also seen along the processes. No correlation was found between the soma size and the density of bradykinin binding. Blocking the bradykinin binding at the B1 receptor with (Des-Arg10)-Lys-bradykinin and at the B2 receptor with D-Arg(Hyp3-Thi5.8-D-Phe7)-bradykinin, respectively, revealed that in 0.75-day-old cultures no or only a very small amount of B1 receptors are present. In 1.75-day-old cultures, the marked increase in the proportion of cells with positive bradykinin binding is due to a de novo expression of the B1 receptor subtype and an up-regulation of the B2 receptor subtype. The selective or combined addition of specific B1 and B2 receptor ligands revealed that both receptor subtypes are co-localized. These data show that cultured sensory neurons express not only B2, but during a short period of time in culture also B1 receptors. The data allow us to hypothesize that a transient increase in bradykinin receptor expression might be caused by cell injury due to disruption of the axon. The injury-induced up-regulation of the receptor in vivo could cause physiological reactions.
内源性九肽缓激肽是一种强效物质，可激活伤害感受器，导致人体产生疼痛感。我们采用一种新开发的非放射性方法，用金标记的缓激肽检测分离的背根神经节细胞中的缓激肽结合位点。在一个细胞亚群中，金标记的缓激肽结合量各不相同。具有缓激肽结合的胞体比例明显取决于培养时间的长短。培养0.75天后，43%的胞体与缓激肽结合。该比例在培养1.75天后增至85%，然后在培养5.75天后降至27%。缓激肽与各种大小的细胞结合，范围从40到2000平方微米，最大为200 - 300平方微米。在一些细胞中，沿突起也可见结合。未发现胞体大小与缓激肽结合密度之间存在相关性。分别用（去精氨酸10）-赖氨酸缓激肽阻断B1受体处的缓激肽结合，用D -精氨酸（Hyp3 - Thi5.8 - D -苯丙氨酸7）缓激肽阻断B2受体处的缓激肽结合，结果显示在0.75日龄的培养物中不存在或仅存在极少量的B1受体。在1.75日龄的培养物中，缓激肽结合阳性细胞比例的显著增加是由于B1受体亚型的从头表达和B2受体亚型的上调。特异性B1和B2受体配体的选择性或联合添加表明两种受体亚型共定位。这些数据表明，培养的感觉神经元不仅表达B2受体，而且在培养的短时间内也表达B1受体。这些数据使我们推测，轴突中断导致的细胞损伤可能引起缓激肽受体表达的短暂增加。体内受体的损伤诱导上调可能导致生理反应。
