Coronary vasoconstriction induced by leukotrienes in the anaesthetized dog

In the anaesthetized dog LTC4, LTD4 (0.3-10 micrograms, injected into the coronary artery) and the thromboxane-mimetic U46619 (5-10 micrograms) decreased coronary blood flow. LTE4 (1-10 micrograms), however, did not affect coronary blood flow. The vasoconstrictor responses to LTC4, LTD4 or U46619 were not altered by the cyclo-oxygenase inhibitor indomethacin (5 mg/kg i.v.). LTC4 and LTD4 did not stimulate the release of any prostaglandin-like substance into the pericardial fluid. It is concluded that LTC4 and LTD4 are able to produce coronary vasoconstriction in vivo independent of the production of any cyclo-oxygenase metabolites of arachidonic acid.