Pratt P F, Hillard C J, Edgemond W S, Campbell W B
Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee 53226, USA.
Am J Physiol. 1998 Jan;274(1):H375-81. doi: 10.1152/ajpheart.1998.274.1.H375.
It has been reported that the endogenous cannabinoid N-arachidonylethanolamide (AEA), commonly referred to as anandamide, has the characteristics of an endothelium-derived hyperpolarizing factor in rat mesenteric artery. We have carried out studies to determine whether AEA affects coronary vascular tone. The vasorelaxant effects of AEA were determined in isolated bovine coronary artery rings precontracted with U-46619 (3 x 10(-9) M). AEA decreased isometric tension, producing a maximal relaxation of 51 +/- 9% at a concentration of 10(-5) M. Endothelium-denuded coronary arteries were not significantly affected by AEA. The CB1 receptor antagonist SR-141716A (10(-6)M) failed to reduce the vasodilatory effects of AEA, suggesting that the CB1 receptor is not involved in this action of AEA. Because AEA is rapidly converted to arachidonic acid and ethanolamine in brain and liver by a fatty acid amide hydrolase (FAAH), we hypothesized that the vasodilatory effect of AEA results from its hydrolysis to arachidonic acid followed by enzymatic conversion to vasodilatory eicosanoids. In support of this hypothesis, bovine coronary arteries incubated with [3H]AEA for 30 min hydrolyzed 15% of added substrate; approximately 9% of the radiolabeled product was free arachidonic acid, and 6% comigrated with the prostaglandins (PGs) and epoxyeicosatrienoic acids (EETs). A similar result was obtained in cultured bovine coronary endothelial cells. Inhibition of the FAAH with diazomethylarachidonyl ketone blocked both the metabolism of [3H]AEA and the relaxations to AEA. Whole vessel and cultured endothelial cells prelabeled with [3H]arachidonic acid synthesized [3H]PGs and [3H]EETs, but not [3H]AEA, in response to A-23187. Furthermore, SR-141716A attenuated A-23187-stimulated release of [3H]arachidonic acid, suggesting that it may have actions other than inhibition of CB1 receptor. These experiments suggest that AEA produces endothelium-dependent vasorelaxation as a result of its catabolism to arachidonic acid followed by conversion to vasodilatory eicosanoids such as prostacyclin or the EETs.
据报道，内源性大麻素N-花生四烯酸乙醇胺（AEA），通常称为花生四烯酸乙醇胺，在大鼠肠系膜动脉中具有内皮源性超极化因子的特征。我们进行了研究以确定AEA是否影响冠状动脉张力。在预先用U-46619（3×10⁻⁹M）预收缩的离体牛冠状动脉环中测定AEA的血管舒张作用。AEA降低等长张力，在10⁻⁵M浓度下产生最大51±9%的舒张。内皮剥脱的冠状动脉对AEA无明显影响。CB1受体拮抗剂SR-141716A（10⁻⁶M）未能降低AEA的血管舒张作用，表明CB1受体不参与AEA的这一作用。因为AEA在脑和肝脏中被脂肪酸酰胺水解酶（FAAH）迅速转化为花生四烯酸和乙醇胺，我们推测AEA的血管舒张作用是由于其水解为花生四烯酸，随后酶促转化为血管舒张性类二十烷酸。支持这一假设的是，用[³H]AEA孵育30分钟的牛冠状动脉水解了15%添加的底物；约9%的放射性标记产物是游离花生四烯酸，6%与前列腺素（PGs）和环氧二十碳三烯酸（EETs）共迁移。在培养的牛冠状动脉内皮细胞中也得到了类似结果。用重氮甲基花生四烯酰基酮抑制FAAH可阻断[³H]AEA的代谢以及对AEA的舒张作用。预先用[³H]花生四烯酸标记的全血管和培养的内皮细胞在A-23187刺激下合成[³H]PGs和[³H]EETs，但不合成[³H]AEA。此外，SR-141716A减弱了A-23187刺激的[³H]花生四烯酸释放，表明它可能具有除抑制CB1受体之外的其他作用。这些实验表明，AEA通过分解代谢为花生四烯酸，随后转化为血管舒张性类二十烷酸如前列环素或EETs，从而产生内皮依赖性血管舒张。
