Changes in lipoxygenase products from synovial fluid in carrageenan induced arthritis in dogs

A non-suppurative chronic arthritis was induced in the juvenile dog knee by intra-articular instillations with Carrageenan. Lipoxygenase products of arachidonic acid were separated from synovial fluid by reversed-phase high-performance liquid chromatography (RP-HPLC). After ten weeks we observed an accumulation of leukotriene B4 (LTB4) in synovial fluid in five out of six experimental knees (0.94 to 5.5 ng/ml), as judged by integrated optical density. Biological activity of LTB4 was confirmed by chemokinesis. LTB4 was not detected in control knees. The 15-lipoxygenase products, 15-hydroxyeicosatetraenoic acid (15-HETE) and 13-hydroxy-9,11-octadecadienoic acid (13-HODD), being inhibitors of 5-lipoxygenase, were found in relatively high levels in the control knees compared to the arthritic knees. The results denote LTB4 as a pro-inflammatory local mediator during carrageenan-induced arthritis; possibly, the decreased levels of 15-HETE and 13-HODD in the arthritic knees may have a regulatory function, thus facilitating LTB4 generation.