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

ABSTRACT

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-PGF1 alpha production was stimulated by AA infusion in a dose-related manner. Infusion of AA at 4 micrograms/ml/min led to an initial production rate of 0.64 +/- 0.29 ng/min which gradually increased to 0.93 +/- 0.11 ng/min at the 20th min of infusion. When the concentration of AA infusion was increased to 10 micrograms/ml/min, 6-keto-PGF1 alpha production increased to 1.14 +/- 0.86 ng/min initially but declined with time. PGE2 production in response to AA 10 micrograms/min/ml was steady at around 5 ng/min while PGF2 alpha and TXB2 production were only slightly above the control. Perfusion of rabbit washed platelet suspensions at a rate of 3 X 10(8) plt/ml/min raised 6KPGF1 alpha production. The production was further increased when platelets were pretreated with 1-benzylimidazole (5 mM), along with a concurrent reduction in TXB2 release. Pretreatment of platelets with aspirin, on the other hand, abolished the increase in 6KPGF1 alpha production. Our data indicated that the vascular smooth muscle cells can efficiently utilize PGH2 produced by platelets to synthesize PGI2.