Houston D S, Shepherd J T, Vanhoutte P M
Am J Physiol. 1985 Mar;248(3 Pt 2):H389-95. doi: 10.1152/ajpheart.1985.248.3.H389.
Aggregating platelets cause an endothelium-dependent relaxation of isolated contracted canine coronary arteries. The role of adenine nucleotides and of 5-hydroxytryptamine in causing this relaxation was determined. Rings of these arteries were suspended in organ chambers filled with physiological salt solution and contracted with prostaglandin F2 alpha. Adenosine diphosphate relaxed rings with intact endothelium but had no effect on endothelium-denuded rings. The relaxation was attenuated by the enzyme, apyrase, which hydrolyzes adenosine tri- and diphosphate. 5-Hydroxytryptamine (5-HT) exerted a direct contractile effect mediated by the endothelium. The latter was prevented by the 5-HT1 serotonergic antagonist, methiothepin, but not by the 5-HT2 serotonergic antagonist, ketanserin. The endothelially mediated relaxation to aggregating platelets was prevented by apyrase but not by methiothepin or ketanserin. Responses to platelets were unaltered by the inhibitor of cyclooxygenase, meclofenamate. These experiments demonstrate the key role of adenine nucleotides in mediating the endothelium-dependent relaxation of canine coronary arteries to aggregating platelets.
聚集的血小板可使离体收缩的犬冠状动脉产生内皮依赖性舒张。研究了腺嘌呤核苷酸和5-羟色胺在引起这种舒张中的作用。将这些动脉环悬挂于充满生理盐溶液的器官浴槽中，并用前列腺素F2α使其收缩。二磷酸腺苷可使内皮完整的动脉环舒张，但对内皮剥脱的动脉环无作用。这种舒张作用可被能水解三磷酸腺苷和二磷酸腺苷的酶——腺苷三磷酸双磷酸酶减弱。5-羟色胺（5-HT）通过内皮介导产生直接收缩作用。5-HT1血清素能拮抗剂美噻吨可阻止这种作用，但5-HT2血清素能拮抗剂酮色林则不能。腺苷三磷酸双磷酸酶可阻止内皮介导的对聚集血小板的舒张作用，但美噻吨或酮色林则不能。环氧化酶抑制剂甲氯芬那酸对血小板反应无影响。这些实验证明了腺嘌呤核苷酸在介导犬冠状动脉对聚集血小板的内皮依赖性舒张中的关键作用。
