Relationship between adenosine-induced vascular effects and ATP-sensitive K+ channels

AIM: To study the relationship between adenosine (Ade) receptors and adenos ine 5'-triphosphate (ATP)-sensitive potassium (K-ATP) channels in rat aorta . METHODS: Isolated rat aorta rings were suspended for isometric force reco rding. The vascular effects of Ade were assessed in the presence or absence of functional endothelium. The interactions of Ade and pinacidil (Pin) or glibenclamide (Gli) were investigated. RESULTS: In isolated aorta preconstr icted with KCl 20 mmol.L-1, Ade 3-300 mu mol.L-1 induced relaxation in a co ncentration-dependent manner; and in 48/99 preparations from 32 rats, Ade i nduced initial transient constriction followed by sustained relaxation. Whe n the functions of K-ATP channels were blocked with Gli 1 or 100 mu mol.L-1 , effects of Ade were characterized by vasoconstriction rather than vasorel axation. The combination of Pin 1 mu mol.L-1 with Ade 100 mu mol.L-1 showed no synergic vasodilatory effects and did not affect Ade-induced vasoconstr iction. After the removal of endothelium, Ade still induced vasoconstrictio n and vasorelaxation, and the constrictive effects showed no difference fro m those in the presence of endothelium, but the potency of vasodilatory eff ects became weaker with slower decrease in tension. CONCLUSION: The activat ion of K-ATP channels is involved in Ade receptor-induced vasodilation.