ATP is involved in myocardial and vascular effects of exogenous bradykininin ejecting guinea pig heart

It has recently been reported that bradykinin induces selective left ventri cular (LV) relaxation in isolated guinea pig hearts via the release of nitr ic oxide. Exogenous bradykinin also induces vasodilation, which is only par tly due to nitric oxide release. In the present study we investigated the r ole of adenyl purines on these bradykinin-induced effects. Isolated ejectin g guinea pig hearts were studied. LV pressure was monitored by a 2-Fr micro manometer-tipped catheter. ATP concentrations were measured using a lucifer in-luciferase assay. Bradykinin (1 and 100 nM) caused a progressive acceler ation of LV relaxation together with a transient increase in coronary flow. These effects were inhibited by the nonselective Pt purinoceptor antagonis t suramin (1 mu M, n = 6) but were unaffected by the selective P-2x purinoc eptor antagonist pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid (1 m u M, n = 6). These myocardial and vascular effects of bradykinin were assoc iated with increased ATP levels in coronary effluent. These data suggest th at the selective enhancement: of LV relaxation and rise in coronary flow in duced by exogenous bradykinin involve endogenous ATP and the subsequent sti mulation of P-2 purinoceptors.