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The present study was an attempt to characterize the adenosine receptor in human coronary arteries, and to establish the dependence of the relaxations mediated by this receptor on a functional endothelium. Human coronary arteries were obtained from organ donors. Adenosine and its analogs (5'-N-ethyl-carboxamido-adenosine, NECA;(More)
Adenosine plays an important role in the regulation of coronary blood flow, as it relaxes the coronary smooth muscle through A2 receptors. Methylxanthines have been used to antagonize the A1 and A2 adenosine receptors in various tissues. The aim of the present study was to investigate the antagonistic profile of methylxanthines towards A2 adenosine receptor(More)
Adenosine relaxes the coronary arteries of various species through A2 receptors. The mechanism(s) by which adenosine causes relaxation of the coronary smooth muscle through changes in intracellular Ca levels is not understood. Therefore, the aim of this study was to evaluate the vasodilatory action of adenosine in normal and in Ca-free medium and the effect(More)
In the present study, we have investigated the changes in calcium influx during the relaxing responses to adenosine and its analogues. Calcium-45 influx was measured in bovine coronary artery rings in the presence of prostaglandin F2 alpha (10(-5) M) and KCl (50 and 100 mM). Prostaglandin F2 alpha and KCl caused increases in calcium influx. Prostaglandin F2(More)
The aim of the present investigation was to evaluate the endothelium dependency in the relaxations by the adenosine analog, 5'-N-ethylcarboxamidoadenosine (NECA), and the requirement for extracellular calcium in endothelium-dependent and independent relaxations. In prostaglandin F2 alpha (PGF2 alpha)-contracted bovine coronary arteries with intact(More)
When the tone is raised by guanethidine, rat anococcygeus muscle produces inhibitory responses to field stimulation, whose mechanism is not understood properly. The present study is an attempt to investigate the role of alpha adrenoceptors in the field stimulation-induced relaxations in isolated rat anococcygeus muscle. When the tissues are contracted with(More)
We have investigated the mechanism of adenosine-induced relaxation in relation to its effects on intracellular organelles in Triton X-100- and saponin-skinned bovine coronary arteries. In intact coronary arteries, high K+ and prostaglandin F2 alpha caused sustained contractions, whereas caffeine produced transient contractions. Triton X-100 treatment(More)
The present study was an attempt to characterize the type of adenosine receptor in human coronary arteries obtained from organ donors with the use of adenosine analogs. Prostaglandin F2 alpha (10(-6) M) produced tonic contractions followed by phasic contractions and diltiazem (10(-6) M) pretreatment changed the phasic contractions to tonic contractions.(More)
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(More)