Boeynaems J M, Heilporn S, Broeders F, Braekman J C
Institute of Interdisciplinary Research, School of Medicine, Université Libre de Bruxelles, Belgium.
Eur J Pharmacol. 1993 Mar 16;233(1):13-20. doi: 10.1016/0014-2999(93)90343-g.
Our observation that loading of bovine aortic endothelial cells with quin 2 or 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) enhances their release of prostacyclin (PGI2) has been studied in detail. The action of the acetoxymethyl ester (AM) of BAPTA (BAPTA-AM) was biphasic: at high concentrations (50 microM) and after prolonged exposure (60 min or more), it behaved as an inhibitor instead of an amplifier. Since inhibition could be related to calcium chelation, we tested 5,5'-difluoro-BAPTA-AM (5FBAPTA-AM), 4,4'-difluoro-BAPTA-AM (4FBAPTA-AM) and 5,5'-dibromo-BAPTA-AM (5BBAPTA-AM), whose corresponding free acids have a reduced affinity for Ca2+: these compounds were much more active in enhancing PGI2 production than BAPTA-AM itself. The effect of 5BBAPTA-AM was detectable at 0.5 microM and almost maximal at 5 microM (5-fold increase). 5BBAPTA-AM increased the release of free arachidonate induced by ATP but had no effect on the generation of inositol phosphates, the release of choline metabolites, and the accumulation of cAMP. 5BBAPTA-AM had a cytotoxic effect on the endothelial cells only after prolonged exposure to a high (50 microM) concentration. 5BBAPTA-AM inhibited the platelet production of thromboxane stimulated by a high (0.5 U/ml) concentration of thrombin and slightly potentiated the effect of a low (0.005 U/ml) concentration. In conclusion, the effect of 5BBAPTA-AM on the production of PGI2 seems to be rather specific to arachidonate metabolism in endothelial cells.
我们观察到，用喹啉2或1,2 - 双（O - 氨基苯氧基）乙烷 - N，N，N'，N' - 四乙酸（BAPTA）加载牛主动脉内皮细胞会增强其前列环素（PGI2）的释放，对此我们进行了详细研究。BAPTA的乙酰氧基甲酯（BAPTA - AM）的作用是双相的：在高浓度（50 microM）和长时间暴露（60分钟或更长时间）后，它表现为抑制剂而非增强剂。由于抑制作用可能与钙螯合有关，我们测试了5,5'-二氟 - BAPTA - AM（5FBAPTA - AM）、4,4'-二氟 - BAPTA - AM（4FBAPTA - AM）和5,5'-二溴 - BAPTA - AM（5BBAPTA - AM），其相应的游离酸对Ca2 +的亲和力降低：这些化合物在增强PGI2生成方面比BAPTA - AM本身更具活性。5BBAPTA - AM在0.5 microM时可检测到其作用，在5 microM时几乎达到最大值（增加5倍）。5BBAPTA - AM增加了ATP诱导的游离花生四烯酸的释放，但对肌醇磷酸的生成、胆碱代谢产物的释放和cAMP的积累没有影响。5BBAPTA - AM仅在长时间暴露于高浓度（50 microM）后才对内皮细胞产生细胞毒性作用。5BBAPTA - AM抑制高浓度（0.5 U/ml）凝血酶刺激的血小板血栓素生成，并略微增强低浓度（0.005 U/ml）的作用。总之，5BBAPTA - AM对PGI2生成的影响似乎对内皮细胞中花生四烯酸代谢具有相当的特异性。
