Cysteinyl leukotrienes act through G-protein-coupled receptors termed cysteinyl leukotriene 1 (CysLT₁) and cysteinyl leukotriene 2 (CysLT₂) receptors. However, little is known about the pathophysiological role of CysLT₂ receptors in asthma. To elucidate the possible involvement of CysLT₂ receptors in bronchoconstriction and airway vascular hyperpermeability, we have established a novel guinea pig model of asthma. In vitro study confirmed that CHO-K1 cells, expressing guinea pig CysLT₂ and CysLT₁ receptors are selectively stimulated by LTC₄ and LTD₄, respectively. However, when LTC₄ was intravenously injected to guinea pigs, the resulting bronchoconstriction was fully abrogated by montelukast, a CysLT₁ receptor antagonist, indicating rapid metabolism of LTC₄ to LTD₄ in the lung. We found that treatment with S-hexyl glutathione (S-hexyl GSH), an inhibitor of gamma-glutamyl transpeptidase, significantly increased LTC₄ content and LTC₄/(LTD₄ plus LTE₄) ratio in the lung. Under these circumstances, LTC₄-induced bronchoconstriction became resistant to montelukast, but sensitive to Compound A, a CysLT₂ receptor antagonist, depending on the dose of S-hexyl GSH. Combination with montelukast and Compound A completely abrogated this spasmogenic response. Additionally, we confirmed that LTC₄ elicits airway vascular hyperpermeability via CysLT₂ receptors in the presence of high dose of S-hexyl GSH as evidenced by complete inhibition of LTC₄-induced hyperpermeability by Compound A, but not montelukast. These results suggest that CysLT₂ receptors mediate bronchoconstriction and airway vascular hyperpermeability in guinea pigs and that the animal model used in this study may be useful to elucidate the functional role of CysLT₂ receptors in various diseases, including asthma.