Influence of fulvic acid on the collagen secretion of bovine chondrocytes in vitro

High concentrations of fulvic acid and selenium deficiency in drinking wate r are the main causative factors of Kashin-Beck disease, an endemic degener ative chronic osteoarticular disorder found in China. The influence of fulv ic acid on collagen secretion was investigated in articular chondrocyte cul tures from bovine interphalangeal joints. Collagen secretion in 7-day-old c hondrocyte monolayers was determined by measuring [H-3]-proline incorporati on into collagen macromolecules after a 24-h application in cultured supern atants. Additionally, collagen secretion was measured with a collagen assay based on a dye-binding method of soluble collagens. Both methods showed a dose-dependent increase of collagen secretion after treatment with fulvic a cid. The collagen was identified by immunoblotting and immunocytochemistry as type II collagen. Fulvic acid also induced H2O2, production in cartilage cells. After co-incubation with catalase and fulvic acid, the cells secret ed the same amount of H2O2 or collagen as the non-treated controls, indicat ing an influence of H2O2 on collagen secretion. Chondrocytes were then trea ted directly with H2O2. This led to increased collagen secretion showing a positive correlation with the concentration of H2O2 up to I pM H2O2. Larger amounts of H2O2 decreased collagen secretion. Effects of reactive oxygen s pecies, such as lipid peroxidation or lactate dehydrogenase (LDH) release f rom damaged cells, were not inducable by fulvic acid (less than or equal to 10 ppm). Our results demonstrate a fulvic-acid-induced stimulation of coll agen secretion into the supernatant by articular chondrocytes via physiolog ical amounts of H2O2.