To examine the possible involvement of lipoxygenase products from arachidonic acid in the pathogenesis of delayed vasospasm after subarachnoid hemorrhage (SAH), we measured the contents of hydroxyeicosatetraenoic acids (HETEs) in the subarachnoid clot, the cerebrospinal fluid, and the basilar artery, using the canine "two-hemorrhage" model. Lipoxygenase activity in the subarachnoid clot and the basilar artery was measured, ex vivo, using samples obtained 7 days after SAH. For a quantitative analysis of HETEs, each sample was homogenized with either ice-cold saline or methanol. The lipid extract was then submitted to reverse-phase HPLC. The identity of each HETE was further confirmed using straight-phase HPLC and gas chromatography-mass spectrometry. When the basilar artery was homogenized with ice-cold saline, a significant increase in the 5-HETE content was observed on SAH day 8. However, when the artery was homogenized with methanol, HETEs were not detected. In the case of incubation in the presence of arachidonic acid and calcium ionophore A23187, the 5-lipoxygenase activity was remarkably increased in the basilar artery exposed to SAH, compared to that of normal dogs. The subarachnoid clot contained a significant amount of 12-HETE (average 1.8 nmol/g wet weight) from day 2 to day 8. The administration of 1,2-bis(nicotinamido)propane significantly ameliorated vasospasm in the two-hemorrhage model, simultaneously inhibiting the 5-lipoxygenase activity of the basilar artery. Our observations show that the activities of 12- and 5-lipoxygenases are significantly increased after SAH in the subarachnoid clot and the basilar artery, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)