Uridine diphosphoglucose dehydrogenase activity in synovial lining cells in the experimental antigen induced model of rheumatoid arthritis: an indication of synovial lining cell function.

Uridine diphosphoglucose dehydrogenase (UDPGD) is the enzyme responsible for the production of uridine diphospho(UDP)-glucuronate, an essential monosaccharide in the biosynthesis of hyaluronan, which is found in high concentrations in normal synovial fluid. Synovial lining cells have been implicated in the synthesis of hyaluronan, but the degree to which they are adapted metabolically to this function in normal and inflamed synovium has not been established. Using a quantitative cytochemical method it was shown that synovial lining cells from chronically inflamed rabbit synovium had significantly lower UDPGD activity per cell than the lining cells of normal synovium. These findings suggest that the lining cells of normal non-inflamed synovium may be enzymatically adapted for the synthesis of hyaluronan and that this may be an indication of a specific role of synovial lining cells in the maintenance of normal joint function.