Martínez M C, Randriamboavonjy V, Ohlmann P, Komas N, Duarte J, Schneider F, Stoclet J C, Andriantsitohaina R
Laboratoire de Pharmacologie et Physico-Chimie des Intéractions Cellulaires et Moléculaires, Unité Mixte de Recherche, Centre National pour les Recherches Scientifiques 7034, Université Louis Pasteur de Strasbourg, Faculté de Pharmacie, France.
Am J Physiol Heart Circ Physiol. 2000 Sep;279(3):H1228-38. doi: 10.1152/ajpheart.2000.279.3.H1228.
The mechanisms of Ca(2+) handling and sensitization were investigated in human small omental arteries exposed to norepinephrine (NE) and to the thromboxane A(2) analog U-46619. Contractions elicited by NE and U-46619 were associated with an increase in intracellular Ca(2+) concentration (Ca(2+)), an increase in Ca(2+)-independent signaling pathways, or an enhancement of the sensitivity of the myofilaments to Ca(2+). The two latter pathways were abolished by protein kinase C (PKC), tyrosine kinase (TK), and Rho-associated protein kinase (ROK) inhibitors. In Ca(2+)-free medium, both NE and U-46619 elicited an increase in tension that was greatly reduced by PKC inhibitors and abolished by caffeine or ryanodine. After depletion of Ca(2+) stores with NE and U-46619 in Ca(2+)-free medium, addition of CaCl(2) in the continuous presence of the agonists produced increases in Ca(2+) and contractions that were inhibited by nitrendipine and TK inhibitors but not affected by PKC inhibitors. NE and U-46619 induced tyrosine phosphorylation of a 42- or a 58-kDa protein, respectively. These results indicate that the mechanisms leading to contraction elicited by NE and U-46619 in human small omental arteries are composed of Ca(2+) release from ryanodine-sensitive stores, Ca(2+) influx through nitrendipine-sensitive channels, and Ca(2+) sensitization and/or Ca(2+)-independent pathways. They also show that the TK pathway is involved in the tonic contraction associated with Ca(2+) entry, whereas TK, PKC, and ROK mechanisms regulate Ca(2+)-independent signaling pathways or Ca(2+) sensitization.
在暴露于去甲肾上腺素（NE）和血栓素A2类似物U-46619的人小网膜动脉中，研究了钙（Ca2+）处理和致敏的机制。NE和U-46619引发的收缩与细胞内钙浓度（[Ca2+]i）增加、钙非依赖性信号通路增加或肌丝对钙的敏感性增强有关。后两种途径被蛋白激酶C（PKC）、酪氨酸激酶（TK）和Rho相关蛋白激酶（ROK）抑制剂消除。在无钙培养基中，NE和U-46619均引起张力增加，PKC抑制剂可大大降低该张力，咖啡因或ryanodine可消除该张力。在无钙培养基中用NE和U-46619耗尽钙储存后，在激动剂持续存在的情况下添加氯化钙会导致[Ca2+]i增加和收缩，尼群地平和TK抑制剂可抑制该收缩，但PKC抑制剂不影响该收缩。NE和U-46619分别诱导42 kDa或58 kDa蛋白的酪氨酸磷酸化。这些结果表明，NE和U-46619在人小网膜动脉中引发收缩的机制包括从ryanodine敏感储存中释放钙、通过尼群地平敏感通道的钙内流以及钙致敏和/或钙非依赖性途径。它们还表明，TK途径参与与钙进入相关的强直性收缩，而TK、PKC和ROK机制调节钙非依赖性信号通路或钙致敏。
