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

Aim: To study the relationship between adenosine (Ade) receptors and adenosine 5'-triphosphate (ATP)-sensitive potassium (KATP) channels in rat aorta.

Methods: Isolated rat aorta rings were suspended for isometric force recording. 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 preconstricted with KCl 20 mmol.L-1, Ade 3-300 mumol.L-1 induced relaxation in a concentration-dependent manner; and in 48/99 preparations from 32 rats, Ade induced initial transient constriction followed by sustained relaxation. When the functions of KATP channels were blocked with Gli 1 or 100 mumol.L-1, effects of Ade were characterized by vasoconstriction rather than vasorelaxation. The combination of Pin 1 mumol.L-1 with Ade 100 mumol.L-1 showed no synergic vasodilatory effects and did not affect Ade-induced vasoconstriction. After the removal of endothelium, Ade still induced vasoconstriction and vasorelaxation, and the constrictive effects showed no difference from those in the presence of endothelium, but the potency of vasodilatory effects became weaker with slower decrease in tension.

Conclusion: The activation of KATP channels is involved in Ade receptor-induced vasodilation.