Fig. 3. Quantification of matrix levels. WI-38 (VA13) or NIH3T3 cells were seeded on 3D or 2D substrates in [35S]methionine labeling medium for 6 hours. Fibronectin was isolated from DOC fractions and culture media, resolved by SDS-PAGE, and quantified by analysis with a phosphorimager. Phosphorimager counts for 3D samples were normalized to 2D samples, which were set to 1 for each sample pair. (A) Relative amounts of DOC-insoluble fibronectin compared to total fibronectin synthesized. (B) Relative amounts of total fibronectin (sum of DOC-soluble, DOC-insoluble and secreted).