Ramagopal M V, Mustafa S J
Department of Pharmacology, School of Medicine, East Carolina University, Greenville, NC 27858-4354.
Can J Physiol Pharmacol. 1990 May;68(5):608-13. doi: 10.1139/y90-088.
Adenosine relaxes the coronary arteries of various species through A2 receptors. The aim of the present investigation was to evaluate the relaxing effects of adenosine in relation to the role of calcium in bovine coronary arteries by studying the vasodilatory effect of adenosine in normal and calcium-free medium and on calcium-45 efflux into calcium-free medium. Acetylcholine (ACh) and norepinephrine (NE) were used to induce tone in coronary artery rings. Adenosine, 5'-(N-ethylcarboxamido)adenosine (NECA), and N6-(L-phenylisopropyl)adenosine (L-PIA) produced concentration-dependent relaxations of the coronary artery rings. Both in normal and calcium-free medium, the order of potency for adenosine analogs (NECA greater than L-PIA greater than adenosine) was similar and 8-phenyltheophylline antagonized the relaxation responses to adenosine and its analogs. Removal of extracellular calcium shifted the concentration-response curves to the right in a parallel fashion, slowed the rate of relaxation, and in NE contracted rings reduced the maximum responses for adenosine and its analogs. In calcium-free medium, adenosine was without an effect on calcium-45 efflux in the presence of ACh. However, adenosine inhibited the stimulated calcium-45 efflux induced by NE. The data suggest that the vasodilatory action of adenosine in bovine coronary smooth muscle has both extracellular calcium-dependent and -independent components.
腺苷通过A2受体使多种物种的冠状动脉舒张。本研究的目的是通过研究腺苷在正常和无钙培养基中的血管舒张作用以及对45钙向无钙培养基中的流出情况，来评估腺苷的舒张作用与钙在牛冠状动脉中的作用之间的关系。使用乙酰胆碱（ACh）和去甲肾上腺素（NE）诱导冠状动脉环产生张力。腺苷、5'-（N-乙基甲酰胺基）腺苷（NECA）和N6-（L-苯异丙基）腺苷（L-PIA）对冠状动脉环产生浓度依赖性舒张作用。在正常和无钙培养基中，腺苷类似物的效力顺序（NECA大于L-PIA大于腺苷）相似，并且8-苯基茶碱拮抗对腺苷及其类似物的舒张反应。去除细胞外钙使浓度-反应曲线平行右移，减慢舒张速率，并且在NE收缩的环中降低了腺苷及其类似物的最大反应。在无钙培养基中，在ACh存在的情况下腺苷对45钙流出没有影响。然而，腺苷抑制由NE诱导的刺激的45钙流出。数据表明，腺苷在牛冠状动脉平滑肌中的血管舒张作用具有细胞外钙依赖性和非依赖性成分。
