[NADPH-diaphorase topochemistry in human and rat knee joint structures and its changes in experimental arthritis]

Using the histochemical demonstration of NADPH-diaphorase (NADPH-d) activity, the distribution of constitutive nitric oxide synthase (NOS) activity was studied in the cartilage and synovium of healthy man and rats and in experimental arthritis. Arthritis was induced in rats by the injection of complete Freund's adjuvant; the material was studied at days 7, 14, 30 and 60 of inflammation. NADPH-d activity was different in man and rat. In human cartilage NADPH-d-positive chondrocytes were absent, whereas in synovium synovial lining cells and endothelial cells of microvessels were marked. In rats of control group and in those treated with adjuvant, high activity of the enzyme was demonstrated in the cytoplasm of proliferating chondroblasts situated in the marginal zone of the cartilage, and in chondrocytes, that formed the isogenous groups in its deep portions. In rat synovium, besides synovial lining and endothelial cells, fibroblasts were also stained. At experimental days 7 and 14 the number of the marked cells with predominantly high enzyme activity increased on the average by approximately 30.4%. This parameter decreased significantly, approaching the control level at day 30, while at day 60 of adjuvant arthritis NADPH-d positive cells were not detected. Heterotopic localization of constitutive NOS indicates that NO is unequally involved in arthritis development in man and rat. The dynamics of enzyme activity depends on the stage of inflammation and determines the specific effect of NO on target cells.