Cysteinyl leukotrienes mediate the response of submucosal ganglia from rat colon to bradykinin

The aim of the present study was to find out the mechanism by which the inflammatory mediator, bradykinin, induces an increase of the cytosolic Ca2+ concentration ([Ca2+]i) in enteric neurons. For this purpose, ganglia in the isolated submucosa from rat colon were loaded with the Ca2+-sensitive dye, fura-2, and were exposed to bradykinin (2 · 10− 8 mol/l). Under control conditions, the kinin evoked a transient increase in [Ca2+]i. Preincubation with quinacrine or arachidonyltrifluoromethylketone (AACOCF3), i.e. blockers of cytosolic phospholipase A2, prevented the raise of [Ca2+]i. This inhibition was mimicked by 5,8,11,14-eicosatetrayonic acid (ETYA), an inhibitor of cyclooxygenases as well as lipoxygenases, and by BWA4C, a selective inhibitor of lipoxygenases, whereas indomethacin was ineffective, suggesting the mediation of the kinin response by a lipoxygenase metabolite. Indeed, a leukotriene, leukotriene D4 (LTD4), mimicked the effect of bradykinin. The LTD4 receptor blocker, MK-571, inhibited the increase in [Ca2+]i evoked by LTD4 and by bradykinin. Consequently, bradykinin receptors in submucosal ganglia from rat colon are coupled to a stimulation of phospholipase A2, the release of arachidonic acid and the production of LTD4, which seems to be finally responsible for the change in the cytosolic Ca2+ concentration.