Ljunggren O, Johansson H, Ljunghall S, Fredholm B B, Lerner U H
Department of Oral Pathology, University of Umeå, Sweden.
J Bone Miner Res. 1991 May;6(5):443-52. doi: 10.1002/jbmr.5650060504.
Recordings of fura-2 fluorescence from single osteoblastic MC3T3-E1 cells showed that bradykinin (BK, 1 microM) induced a rapid increase in cytoplasmic free Ca2+ (Cai2+, from 114 +/- 13 to 239 +/- 17 nM, mean +/- SEM). Following this initial transient (less than 1 minute) increase there was a second slow increase in Cai2+ (from 117 +/- 11 to 151 +/- 12 nM). Incubation in buffer with no Ca2+ did not affect the first rapid BK-induced increase in Cai2+ but eliminated the second slow increase. Addition of indomethacin or hydrocortisone to the incubation buffer did not inhibit the effect of BK on Cai2+. BK caused a dose-dependent initial rapid increase in Cai2+ with threshold at 1 nM and a maximal effect (241 +/- 30% of basal Cai2+ concentration) at 0.1 microM. The B1 BK receptor agonist des-Arg9-BK (1 microM) caused only a small increase in Cai2+ in MC3T3-E1 cells (from 101 +/- 20 to 140 +/- 4 nM). BK dose and time dependently stimulated the formation of inositol phosphates in MC3T3-E1 cells with EC50 at 2.4 nM and a significant increase in inositol trisphosphate already seen after 15 s. The Ca2+ ionophore ionomycin induced a rapid increase in Cai2+ and prostaglandin E2 (PGE2) formation in MC3T3-E1 cells. Forskolin (10-30 microM) increased cyclic AMP accumulation but did not affect Cai2+ or PGE2 formation. Depletion of extracellular Ca2+ significantly reduced (but did not abolish) BK-induced PGE2 formation. The initial action of BK on Cai2+ is probably due to an inositol-(1,4,5)-trisphosphate-mediated rapid release of Ca2+ from intracellular stores in osteoblasts and is followed by an influx of extracellular Ca2+. The effect is due to B2 BK receptor occupancy and is not secondary to the prostaglandin synthesis. The BK-induced breakdown of phosphatidylinositol-(4,5)-bisphosphate with a subsequent increase in Cai2+ may be involved in BK-induced prostaglandin formation in osteoblasts.
对单个成骨细胞MC3T3-E1细胞进行的fura-2荧光记录显示，缓激肽（BK，1微摩尔）可诱导细胞质游离Ca2+（Cai2+）迅速升高（从114±13纳摩尔升至239±17纳摩尔，平均值±标准误）。在这一初始短暂升高（不到1分钟）之后，Cai2+出现第二次缓慢升高（从117±11纳摩尔升至151±12纳摩尔）。在无Ca2+的缓冲液中孵育不影响BK诱导的Cai2+的首次快速升高，但消除了第二次缓慢升高。向孵育缓冲液中添加吲哚美辛或氢化可的松并不抑制BK对Cai2+的作用。BK引起Cai2+剂量依赖性的初始快速升高，阈值为1纳摩尔，在0.1微摩尔时达到最大效应（基础Cai2+浓度的241±30%）。B1 BK受体激动剂去-Arg9-BK（1微摩尔）仅使MC3T3-E1细胞中的Cai2+略有升高（从101±20纳摩尔升至140±4纳摩尔）。BK剂量和时间依赖性地刺激MC3T3-E1细胞中肌醇磷酸的形成，EC50为2.4纳摩尔，15秒后已观察到肌醇三磷酸显著增加。Ca2+离子载体离子霉素可诱导MC3T3-E1细胞中Cai2+和前列腺素E2（PGE2）的快速形成。福斯高林（10 - 30微摩尔）增加环磷酸腺苷的积累，但不影响Cai2+或PGE2的形成。细胞外Ca2+的耗竭显著降低（但未消除）BK诱导的PGE2形成。BK对Cai2+的初始作用可能是由于肌醇-（1,4,5）-三磷酸介导的成骨细胞内Ca2+从细胞内储存库的快速释放，随后是细胞外Ca2+的内流。该效应是由于B2 BK受体被占据，并非继发于前列腺素合成。BK诱导的磷脂酰肌醇-（4,5）-二磷酸的分解以及随后Cai2+的增加可能参与了BK诱导的成骨细胞中前列腺素的形成。
