Prostaglandin biosynthesis by lapine articular chondrocytes in culture

Abstract

Secondary monolayer and spinner cultures of rabbit articular chondrocytes released into the culture medium prostaglandins the synthesis of which was inhibited by sodium meclofenamate. The prostaglandins measured by radioimmunoassay were, in order of decreasing abundance, prostaglandin E 2, 6-oxoprostaglandin F 1α, (the stable metabolite of prostacyclin) and prostaglandin F 2α. Several lines of evidence indicated that chondrocytes synthesize little if any thromboxane B 2 (the stable metabolite of thromboxane A 2). The presence of prostaglandins was confirmed by radiometric thin-layer chromatography of extracts of culture media incubated with [ 3H]arachidonic acid-labeled cells. In monolayer culture, chondrocytes synthesized immunoreactive prostaglandins in serum-free as well as serum-containing medium. Monolayer chondrocytes produced higher levels of prostaglandin E 2 relative to 6-oxo-prostaglandin F 1α than did spinner cells, but the latter synthesized more total prostaglandins. The identity of endogenous prostaglandins as well as those synthesized in short-term culture by rabbit cartilage slices was compared to those produced by chondrocytes in long-term culture. Chondrocytes synthesized all of the prosta-glandins found in articular cartilage. Minimal quantities of thromboxane B 2 were detected in cartilage. A higher percentage of 6-oxo-prostaglandin F 1α relative to other prostaglandins was found in cartilage than in either monolayer or spinner chondrocyte cultures. These results demonstrate that articular chondrocytes synthesize prostaglandins and prostacyclin. These prostaglandins may exert significant physiological effects on cartilage, since exogenous prosta-glandins depress chondrocyte sulfated-proteoglycan synthesis and may even promote proteoglycan degradation.