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Objective. To investigate the role of cytokines and growth factors in the regulation of hyaluronan synthesis in human synovial lining cells.Methods. Synovial lining cells were obtained from human knee joints, isolated by the explant method, and characterized by immunocytochemistry using monoclonal antibodies against monocytehnacrophage markers as well as antibodies against hyaluronan synthase. After stimulation by cytokines and growth factors, hyaluronan was measured by radiometric assay. The molecular weight distribution of the hyaluronan synthesized was determined by high-performance gelpermeation liquid chromatography. To test the effect of oxygen-derived free radicals, the concentration and molecular weight distribution of hyaluronan were determined in the presence and absence of catalase and superoxide dismutase.Results. Hyaluronan synthesis was stimulated in synovial lining cells by transforming growth factor Pl (TGFPl), interleukin-lp (IL-lp), and to a lesser extent by tumor necrosis factor a (TNFa). Analysis of the molecular weight distribution of hyaluronan after stimulation of synovial lining cells with TGFP1, IL-lP, and TNFa indicated that hyaluronan is synthesized in a high molecular weight form and might be degraded in the course of inflammatory processes by oxygen-derived free radicals. Conclusion. Our findings suggest that TGFPl is aSupported in part by grant 01 VM 891516 from the Bundesminister fur Forschung und Technologie (BMFT),

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Summary: A method was developed for the simultaneous determination of hypoxanthine, xanthine, uric acid and allantoin based on isocratic reversed-phase chromatography. This HPLC-method additionally allows the direct determination with UV-detection of inosine-5'-phosphate, uridine, thymine, orotic acid, allopurinol and oxipurinol, besides hypoxanthine, xanthine and uric acid in the same Chromatographie run. Allantoin elutes in this system near the void volume and a fraction is collected covering the retention time range for this substance. After hydrolysis allantoin is converted to glyoxylate-2,4-dinitrophenylhydrazone, rechromatographed and detected at 360 nm.The coefficient of variation for this method does not exceed 5.0% for a serum concentration of 0.3 μηιοΙ/1 hypoxanthine and is not greater than 5.3% for a xanthine concentration of 0.3 μιηοΐ/ΐ serum. Recoveries were 90-110% for both hypoxanthine and xanthine. The determination of uric acid had an imprecision and inaccuracy not exceeding 1.45% in the concentration range of 103 -568 μιηοΐ/ΐ. Due to the more complex procedure required for the determination of allantoin, the coefficient of variation between days was 13.6% for a sample containing 0.8 μπιοΐ/l allantoin and the recoveries for this analyte were in the range of 86 -93%.Reference ranges (mean ± SD) determined on 171 serum samples from healthy adults were 12.7 ± 6.6 μιηοΐ/ΐ for hypoxanthine, 3.3 ±1.4 μιηοΐ/ΐ for xanthine, and 15.7 ± 7.9 μιηοΐ/ΐ for allantoin. No significant age or sex dependence was observed. Uric acid concentrations were 320 ± 55 μιηοΐ/l serum for men and 206 ± 55 μιηοΐ/ΐ for women.

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