Eicosapentaenoic acid (EPA) is converted to epoxyeicosatetraenoic acids (EpETEs) by several cytochrome P450 isoforms. The major product of this epoxygenase pathway, (±) 17 (18) -EpETE, relaxes vascular and airway smooth muscle by activating large conductance Ca2+-activated K+ (BKCa) channels by directly interacting with BKα channel subunits. (±) 8 (9) -EpETE is an epoxygenase pathway product produced from EPA by CYP450 both in vitro and in vivo.