The actions of leukotrienes C4 and D4 on guinea-pig isolated hearts.

1 Infusions of leukotrienes C4 (LTC4) and LTD4 (5 min; 4 X 10-10-2 X 10-8 M) produced dose-dependent decreases in coronary flow in Langendorff preparations of guinea-pig isolated heats. 2 LTC 4 was more active than LTD4 and produced 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 X 10-5 M) inhibited the effects of LTC4 but only reduced the initial LTD4- induced effects. 6 The effects of FPL 55712 (3.8 X 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.