[Effect of thromboxane A2 synthetase inhibitor (OKY-046) on leukotriene C4-induced airway hyperresponsiveness in guinea pigs].

In this study, we investigated the effects of peroral (p.o.) administration of a thromboxane A2 (TXA2) synthetase inhibitor, OKY-046, on the airway hyperresponsiveness (AHR) in guinea pigs induced by intravenous administration of leukotriene C4 (LTC4). A 3 micrograms/kg/hr LTC4 infusion induced airway wall thickening (AWT) and AHR to 1.8 and 3.6 micrograms/kg histamine bolus shot. OKY-046 100 mg/kg p.o. partially inhibited the AHR induced by LTC4 without inhibition of AWT. Previously, we have reported that LTC4-induced AHR was partially inhibited, to the same exert as by OKY-046, by TXA2 receptor antagonists, ONO-NT-126 and ONO-8809. These data suggest that intravenous administration of LTC4 generates TXA2, and TXA2 augments LTC4-induced AHR partially in guinea pigs.