RESUMO
The fate of RNA revealed by metachromatic staining after a critical electrolyte concentration assay using toluidine blue and Mg(2+)ions as competitors for the substrate dye binding sites was followed at mitosis in human breast epithelial cells transformed by benzo[a]pyrene and transfected with the c-Ha- ras oncogene. The aim was to detect changes in RNA distribution during mitosis in human transformed/tumorigenic cells exhibiting increased nucleolar sizes and rRNA production while in interphase. RNA relocation in association with the mitotic spindle fibers was observed from metaphase to telophase not to vary in all the cell lines studied. RNA-containing nucleolus-like bodies persistent during mitosis were found to decrease in frequency in the transformed and tumorigenic cells in comparison with control non-transformed cells simultaneously to the previously reported increase in nucleolar areas for the same cells while in interphase. It is suggested that an improved use of RNA transcripts has been developed with cell transformation and tumorigenesis in this particular model.