[Effects of thromboxane on pulmonary arterial response to platelet activating factor in rabbit]

The aim of this study is to clarify whether thromboxane mediates hemodynamic and airway changes induced by PAF in rabbits. Rabbits were divided into 4 groups. In No group rabbits (n = 5), PAF was intravenously injected. In Indo group rabbits (n = 5), indomethacin was infused intravenously 20 min prior to PAF administration. In KT2 group rabbits (n = 4), selective thromboxane antagonist; KT2-962, or in CV group rabbits (n = 3), selective PAF antagonist; CV6209 was injected intravenously 5 min prior to PAF administration. After PAF administration, pulmonary arterial and airway pressures increased transiently, and blood pressure, and leukocyte as well as platelet counts decreased. These hemodynamic and airway changes induced by PAF were almost totally blocked by CV6209 administration, but not by indomethacin and KT2-962 administrations. Similarly, decreases in leukocyte and platelet counts induced by PAF were blocked by CV6209 and KT2-962, but not by indomethacin. We conclude that thromboxane does not mediate hemodynamic and airway changes induced by PAF. PAF is likely to directly induce these changes.