Oike M, Droogmans G, Nilius B
KU Leuven, Laboratorium voor Fysiologie, Belgium.
Proc Natl Acad Sci U S A. 1994 Apr 12;91(8):2940-4. doi: 10.1073/pnas.91.8.2940.
We have investigated the changes in intracellular calcium concentration ([Ca2+]i) in human endothelial cells induced by mechanical stretch due to osmotic cell swelling. Hypotonic solutions also activate a Cl- conductance that has been described elsewhere and mainly serves to clamp the membrane potential at negative values to provide a driving force for Ca2+ influx. The increase in [Ca2+]i caused by hypotonic solutions is due to release from inositol-1,4,5-trisphosphate-sensitive Ca2+ pools and a subsequent Ca2+ influx, apparently activated by store depletion. These changes in [Ca2+]i are completely abolished if the phospholipase A2 (PLA2) activity is inhibited by either 4-bromophenacyl bromide or cyclosporin A. Arachidonic acid, applied either extracellularly or intracellularly via the patch pipette, mimics the mechanosensitive response even in cells with blocked PLA2. Metabolites of the lipo- and cyclooxygenase pathways can be excluded. Phospholipase C activation and the protein kinase A pathway are not involved in this mechanical response. Although no specific pharmacological tools for probing the role of PLA2 are available, our evidence suggests that mechanosensitivity in endothelial cells may be modulated by arachidonic acid.
我们研究了由于渗透性细胞肿胀导致的机械拉伸所诱导的人内皮细胞内钙浓度（[Ca2+]i）的变化。低渗溶液还会激活一种氯离子电导，这在其他地方已有描述，其主要作用是将膜电位钳制在负值，为钙离子内流提供驱动力。低渗溶液引起的[Ca2+]i升高是由于从肌醇-1,4,5-三磷酸敏感的钙库释放以及随后的钙离子内流，这显然是由钙库耗竭激活的。如果磷脂酶A2（PLA2）活性被4-溴苯甲酰溴或环孢素A抑制，[Ca2+]i的这些变化会完全消除。通过膜片吸管在细胞外或细胞内施加花生四烯酸，即使在PLA2被阻断的细胞中也能模拟机械敏感反应。脂氧合酶和环氧化酶途径的代谢产物可以排除在外。磷脂酶C激活和蛋白激酶A途径不参与这种机械反应。尽管没有用于探究PLA2作用的特异性药理学工具，但我们的证据表明内皮细胞的机械敏感性可能受花生四烯酸调节。
