Influence of adenosine triphosphate on the isolated perfused mesenteric artery of the rabbit

The vascular effects of adenosine triphosphate (ATP) were examined in the isolated perfused mesenteric arteries of the rabbit. Bolus injections of ATP (1 X 10(-8) to 10(-6) mol) induced a dose-dependent vasoconstrictor response at resting perfusion pressure, while continuous perfusion with ATP briefly elicited a vasoconstrictor response which was not maintained. Perfusion with phentolamine (2.65 X 10(-6) M, an alpha-adrenergic receptor blocker), indomethacin (8.37 X 10(-6) M, an inhibitor of cyclooxygenase), atropine (1 X 10(-7) M, a muscarinic receptor blocker), and hydralazine (2 X 10(-4) M, a vascular smooth muscle inhibitor) for a period of 1 h had no effect on vasoconstrictor responses to ATP. However, pretreatment with reserpine (2 mg X kg-1 X day-1 for 2 days), an agent which depletes catecholamines, potentiated responses to ATP. On the other hand, when vascular tone was increased with an isoosmotic 60 mM K+ depolarizing Krebs bicarbonate solution, bolus injections of ATP elicited a prominent dose-dependent vasoconstriction followed by a prominent vasodilation. The degree of vasodilation but not of vasoconstriction elicited by ATP was greater in small terminal arteries with branches (less than 0.5 mm outside diameter (o.d.) ) than in the medium size arteries (less than or equal to 1 mm o.d.) without terminal branches. Both the vasoconstrictor and vasodilator responses were unaffected by a perfusion with atropine, indomethacin, or eicosatetraynoic acid (ETYA, 1 X 10(-4) M) for 1-2 h.(ABSTRACT TRUNCATED AT 250 WORDS)