Whorton A R, Collawn J B, Montgomery M E, Young S L, Kent R S
Biochem Pharmacol. 1985 Jan 1;34(1):119-23. doi: 10.1016/0006-2952(85)90109-1.
To investigate the hypothesis that cyclic AMP (cAMP) regulates arachidonic acid metabolism in vascular tissue, we have studied the effects of forskolin (FSK), an activator of adenylate cyclase, and 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor, on hormone-stimulated prostacyclin (PGI2) synthesis in porcine aortic endothelial cells grown in culture. In these experiments, bradykinin (1 microgram/ml) and A23187 (0.2 microM) potently stimulated PGI2 biosynthesis (9- and 10-fold respectively). However, prostaglandin synthesis in response to either of these agents was not affected by FSK even though FSK elevated intracellular levels of cAMP 10-fold. IBMX failed to elevate basal cAMP levels when incubated with unstimulated cells. Stimulation of IBMX-treated (0.1 but not 1.0 or 4.0 mM) cells with bradykinin, however, did result in increased cAMP levels, presumably due to PGI2 formation and subsequent activation of adenylate cyclase. In addition to phosphodiesterase inhibition, IBMX inhibited PGI2 formation (72% at 1 mM) in a dose-dependent manner so that, at higher doses of IBMX, cAMP levels returned to baseline. Thus, prostacyclin synthesis inhibition by IBMX could not be attributed to elevated cAMP. In other experiments, IBMX (1 mM) was found to directly inhibit arachidonic acid release (32%) and arachidonic acid metabolism (65%) in endothelial cells and to inhibit arachidonic acid conversion to PGE2 by sheep seminal vesicle microsomes (65%). These data suggest that IBMX directly inhibits both phospholipase and cyclooxygenase activities. These experiments do not support the contention that cAMP regulates these enzymes in cultured aortic endothelial cells.
为了研究环磷酸腺苷（cAMP）调节血管组织中花生四烯酸代谢这一假说，我们研究了腺苷酸环化酶激活剂福斯高林（FSK）和磷酸二酯酶抑制剂3-异丁基-1-甲基黄嘌呤（IBMX）对培养的猪主动脉内皮细胞中激素刺激的前列环素（PGI2）合成的影响。在这些实验中，缓激肽（1微克/毫升）和A23187（0.2微摩尔）能有效刺激PGI2生物合成（分别为9倍和10倍）。然而，尽管FSK使细胞内cAMP水平升高了10倍，但这两种物质中任何一种所引发的前列腺素合成均不受FSK影响。将IBMX与未受刺激的细胞一起孵育时，它未能提高基础cAMP水平。不过，用缓激肽刺激经IBMX处理（0.1毫摩尔而非1.0或4.0毫摩尔）的细胞时，确实导致cAMP水平升高，这可能是由于PGI2形成以及随后腺苷酸环化酶的激活所致。除了抑制磷酸二酯酶外，IBMX还以剂量依赖的方式抑制PGI2形成（1毫摩尔时为72%），因此，在较高剂量的IBMX作用下，cAMP水平恢复到基线。所以，IBMX对前列环素合成的抑制不能归因于cAMP升高。在其他实验中，发现IBMX（1毫摩尔）能直接抑制内皮细胞中花生四烯酸的释放（32%）和花生四烯酸代谢（65%），并抑制绵羊精囊微粒体将花生四烯酸转化为PGE2的过程（65%）。这些数据表明，IBMX直接抑制磷脂酶和环氧化酶的活性。这些实验不支持cAMP调节培养的主动脉内皮细胞中这些酶的观点。
