Automation of mouse micronucleus genotoxicity assay by laser scanning cytometry

Background: The evaluation of the safety of drugs and other chemicals is an important aspect of toxicology work. The mouse micronucleus assay is a sta ndard in vivo genotoxicity assay. Chromosomal damage is an indicator of gen otoxicity, which manifests in the formation of micronuclei in polychromatic erythrocytes from bone marrow and in peripheral blood erythrocytes. The as say is laborious to perform by manual counting. The laser scanning cytomete r allows automated and rapid quantitation of cellular and subcellular fluor escence in monodisperse cell samples on a microscope slide. The object of t his study was to evaluate the application of this new technology in the mou se micronucleus genotoxicity assay. Materials and Methods: One hundred ferry-four mice of various strains were dosed with combinations of carcinogens and antioxidants. Duplicate blood fi lms were prepared 3 days later. One set: of slides was stained with acridin e orange, and the proportion of micronucleated erythrocytes was counted in 5,000 cells per slide. The duplicates were stained with propidium iodide (4 0 mug/ml). Five thousand cells per sample were examined using a laser scann ing cytometer. The proportion of micronucleated erythrocytes was measured. Results: A coefficient of correlation of 0.96 was found between the data fr om the two assays. The automation of the assay on the LSC produced a consid erable time saving and efficiency gain. Conclusions: We conclude that with further development, laser scanning cyto metry is likely to become the preferred modality for the performance of sta ndard genotoxicity assays. Cytometry 44:153-155, 2001. (C) 2001 Wiley-Liss, Inc.