Fluorometric assay of DNA in cartilage and correction for interference by matrix components

A fluorometric assay using 3,5-diaminobenzoic acid for analysis of DNA in alkaline-hydrolyzed calf articular cartilage is described. Additional estimates of DNA content, obtained by counting of cells in cartilage slices and of cells isolated from the tissue by digestion with bacterial collagenase, indicated that falsely high values were obtained with the fluorometric assay and with the indole procedure of Bonting and Jones. Cartilage collagen and proteoglycan were both found to contribute to this interference. Factors to correct for this interference were determined, based upon the hydroxyproline and uronic acid contents of these components. application of these corrections to DNA values obtained by fluorometric assay of the cartilage samples resulted in DNA estimates in agreement with those obtained by counting of cells.