Production of eicosanoids by deendothelialized rabbit aorta: interaction between platelets and vascular wall in the synthesis of prostacyclin

Production of eicosanoids by deendothelialized aorta in response to continuous infusions of arachidonic acid and platelet suspensions was determined in a rabbit aorta perfusion model. 6-keto-PGF_1α production was stimulated by AA infusion in a dose-related manner. Infusion of AA at 4 μ/ml/min led to an initial production rate of 0.64±0.29 ng/min which gradually increased to 0.93±0. ll ng/min at the 20th min of infusion. When the concentration of AA infusion was increased to 10 μg/ml/min, 6-keto-PGF_1α production increased to 1.14±0.86 ng/min initially but declined with time. PGE₂ production in response to AA 10 μg/min/ml was steady at around 5 ng/min while PGF_2α and TXB₂ production were only slightly above the control Perifusion of rabbit washed platelet suspensions at a rate of 3X10⁸ plt/ml/min raised 6KPGF_1α production. The production was further increased when platelets were pretreated with 1-benzylimidazole (5 mM), along with a concurrent reduction in TXB₂ release. Pre-treatment of platelets with aspirin, on the other hand, abolished the increase in 6KPGF_1α production. Our data indicated that the vascular smooth muscle cells can efficiently utilize PGH₂ produced by platelets to synthesize PGI₂.