Prostaglandins in the rheumatic diseases.

The prostaglandins may participate in the pathogenesis of the inflammatory rheumatic diseases by acting as mediators of inflammation and in promoting bone resorption. Levels of PGB (presumed to arise from PGE) in synovial fluids are elevated in the majority of a group of patients with inflammatory rheumatic diseases, as compared to similar patients treated with aspirin and indomethacin and patients with osteoarthritis. Rheumatoid synovium produces large amounts of PGE2 in organ culture. In addition, fibroblast cell lines derived from rheumatoid synovia synthesize more PGE and more cAMP than do cells from normal synovia or skin. The media from rheumatoid synovial organ cultures contain large quantities of bone-resorbing activity toward mouse calvaria in vitro. The bone resorption can be accounted for by PGE2 produced by the synovia, because the activity and PG synthesis are inhibited by more than 90% by incubation of the tissue with indomethacin, because it is quantitatively extractable into ether, and because it bears a relationship to the concentrations of PGE2 present, as measured by radioimmunoassay.