THE ACTIONS OF LEUKOTRIENES C4 AND D4 ON GUINEA‐PIG ISOLATED HEARTS

1 Infusions of leukotrienes C4 (LTC4) and LTD4 (5 min; 4 × 10−10‐2 × 10−8 m) produced dose‐dependent decreases in coronary flow in Langendorff preparations of guinea‐pig isolated hearts. 2 LTC4 was more active than LTD4 and produced a greater reduction in coronary flow. 3 LTC4 and LTD4 also caused reduction in contractility in perfused hearts but not in isolated atria or driven ventricular strips. 4 There was a greater reduction in contractility to LTD4 compared with LTC4 at doses which produced approximately 50% reduction in coronary flow. 5 Indomethacin (1.4 × 10−5 m) inhibited the effects of LTC4 but only reduced the initial LTD4‐induced effects. 6 The effects of FPL 55712 (3.8 × 10−6 m) were similar to those of indomethacin. 7 LTC4 and LTD4 may therefore contribute to the abnormalities of cardiac function that occur in immediate hypersensitivity reactions, particularly reduction in coronary flow.