Cyclooxygenase products of arachidonic acid metabolism by mouse bone in organ culture

Abstract

The products of endogenous and exogenous arachidonic acid metabolism via the cyclooxygenase pathway in mouse bone in organ culture were identified and quantitated by the use of high performance liquid chromatography and radioimmunoassay. Production of prostaglandins E 2, F 2α, and I 2 from endogenous substrate was stimulated by incubation of bone with epidermal growth factor and the tumor promoter 12- O-tetradecanoyl-phorbol-13-acetate. Addition of arachidonic acid to the culture medium not only resulted in the accumulation of prostaglandins E 2, F 2α, and I 2 but also thromboxane. Bone metabolized prostaglandins E 2 and F 2α to their respective 13,14-dihydro-15-ketoderivatives. Prostaglandin I 2, measured as 6-keto-prostaglandin F 1α was synthesized by bone, and metabolic products of prostaglandin I 2 or 6-keto-prostaglandin F 1α, either 6,15-dike to-prostaglandin F 1α or 13,14-dihydro-6,15-diketoprostaglandin F 1α, were also detected in the culture media. Formation of cyclooxygenase products of endogenous and exogenous arachidonic acid metabolism (both basal and stimulated) and bone resorption were inhibited by indomethacin. Bone as a tissue responded biochemically not only to exogenous prostaglandins and agents that enhance endogenous prostaglandin production but also to exogenous arachidonic acid by biosynthesis of prostaglandins, prostacyclin and thromboxane. Furthermore, bone metabolized these cyclooxygenase products to their more stable metabolites.