The influence of embedding on the stoichiometry of the pararosaniline-Feulgen stain in histological material.

In the present study the influence of the embedding technique on the dye-substrate-interaction of the Feulgen reagent has been investigated. Pieces of rat liver and of human lung tumours were fixed in formaline, Carnoy's or Bouin's solution or in SuSa and embedded in paraffin (P) or in glycolmethacrylate (GMA). Sections were stained with the pararosaniline-Feulgen-reagent. Mean optical density (MOD) of cell nuclei was measured with an image analyzer. GMA required longer times for hydrolysis and staining than P. the plateau phase of acid hydrolysis was longer in GMA. In general MOD was significantly lower in GMA than in P. The ratio of MOD of lymphocyte nuclei versus diploid basal cell nuclei in lung tissue was 0.97 in GMA and 0.88 in P, respectively. We presume that cross-linking of GMA monomers during polymerization stabilizes hydrolysed DNA. Steric factors are responsible for the slow diffusion of the dye-molecule. The influence of the embedding medium on the stoichiometry of the Feulgen stain has to be carefully considered for statistical evaluation of DNA-histograms.