Mathis S A, Criscimagna N L, Leeb-Lundberg L M
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760, USA.
Mol Pharmacol. 1996 Jul;50(1):128-39.
Stimulation of B1 and B2 kinin receptors on cultured rabbit superior mesenteric artery smooth muscle cells with des-Arg9-bradykinin (DBK) and bradykinin (BK), respectively, results in significantly different patterns of intracellular Ca2+ mobilization. Single-cell fluorescence imaging of Fura-2-loaded cells revealed that although both DBK and BK initially triggered similar rapid increases in cytosolic free Ca2+, the DBK response was biphasic and sustained, whereas the BK response was transient. The DBK response was maintained for > or = 20 min with the second phase characterized by an elevated plateau and/or base-line oscillations. The BK response was limited to an initial transient peak with the exception of a few cells, which after a prolonged latency period, exhibited weak but regular base-line oscillations. The initial BK- and DBK-stimulated rises in cytosolic free Ca2+ were dependent on the release of Ca2+ from intracellular stores that seemed to be common for the two agonists. On the other hand, the continuation of the sustained phase of the DBK response required the influx of extracellular Ca2+, as well as continuous receptor occupancy by the agonist. Stimulation of cells with DBK followed by washing and restimulation with the same agonist within < or = 2 min resulted in a second B1 receptor response that was not significantly different from the first response. In contrast, the same protocol with BK yielded a dramatically decreased second B2 receptor response. This attenuation did not seem to be due to a lack of Ca2+ in the agonist-sensitive intracellular stores because DBK elicited a full response after BK stimulation. This study shows that in single cultured RSMA smooth muscle cells, agonist stimulation of B1 receptors generates a sustained intracellular Ca2+ signal, whereas stimulation of B2 receptors promotes rapid and homologous desensitization, resulting in a transient Ca2+ signal. These distinct receptor-specific patterns of Ca2+ mobilization imply significantly different roles for B1 and B2 kinin receptors in vascular smooth muscle cells.
分别用去精氨酸9 - 缓激肽（DBK）和缓激肽（BK）刺激培养的兔肠系膜上动脉平滑肌细胞上的B1和B2激肽受体，会导致细胞内Ca2 +动员模式显著不同。对负载Fura - 2的细胞进行单细胞荧光成像显示，尽管DBK和BK最初均引发了胞质游离Ca2 +的类似快速增加，但DBK反应是双相且持续的，而BK反应是短暂的。DBK反应持续≥20分钟，第二阶段的特征是高原期升高和/或基线振荡。BK反应仅限于初始的短暂峰值，少数细胞除外，这些细胞在延长的潜伏期后表现出微弱但规则的基线振荡。最初由BK和DBK刺激引起的胞质游离Ca2 +升高依赖于细胞内储存的Ca2 +释放，这两种激动剂似乎都有此现象。另一方面，DBK反应持续阶段的持续需要细胞外Ca2 +的流入以及激动剂对受体的持续占据。在≤2分钟内用DBK刺激细胞，然后洗涤并用相同激动剂再次刺激，会产生第二个B1受体反应，该反应与第一个反应无显著差异。相比之下，相同的方案应用于BK时，会使第二个B2受体反应显著降低。这种衰减似乎不是由于激动剂敏感的细胞内储存中缺乏Ca2 +，因为BK刺激后DBK仍能引发完全反应。这项研究表明，在单个培养的兔肠系膜上动脉平滑肌细胞中，激动剂刺激B1受体产生持续的细胞内Ca2 +信号，而刺激B2受体则促进快速同源脱敏，导致短暂的Ca2 +信号。这些不同的受体特异性Ca2 +动员模式意味着B1和B2激肽受体在血管平滑肌细胞中具有显著不同的作用。
