8-Epi-prostaglandin F2alpha (8-epi-PGF2alpha) is an F2-isoprostane formed mainly via noncyclooxygenase pathways in vivo. We investigated whether 8-epi-PGF2alpha has any effect on airflow obstruction and plasma exudation in vivo. Airflow obstruction was quantified by measuring lung resistance (RL) in anesthetized and ventilated guinea pigs, and plasma exudation was quantified by the Evans Blue dye method (20 mg/kg intravenously). Intratracheal instillation of 8-epi-PGF2alpha (1 nmol or 10 nmol) caused dose-related increases in RL. Furthermore, the higher dose of 8-epi-PGF2alpha produced Evans Blue dye extravasation in main bronchi and intrapulmonary airways. A prostanoid TP-receptor antagonist, BAY u3405 (1 mg/kg intravenously), abolished the airway effects of 8-epi-PGF2alpha (10 nmol). A thromboxane A2 (TxA2) synthase inhibitor, OKY-406 (30 mg/kg intravenously), significantly attenuated these effects of 8-epi-PGF2alpha (10 nmol). The level of TxB2, a stable TxA2 metabolite, increased in bronchoalveolar lavage fluid (BALF) after 8-epi-PGF2alpha instillation. We conclude that 8-epi-PGF2alpha causes airflow obstruction and plasma exudation in vivo. This effect may be mediated primarily via prostanoid TP-receptors, and a secondary generation of TxA2 may be involved in part of the airway responses in 8-epi-PGF2alpha in the guinea pig.