USE OF ACRIDINE-ORANGE IN - FLOW CYTOMETRIC ASSESSMENT OF MICRONUCLEIINDUCTION

The micronucleus assay is a widely accepted method for evaluation of c lastogens and aneugens. In the current study, acridine orange (AO) sup ravital staining was adapted for flow cytometric usage to assess micro nucleated cells in rat bone marrow and spleen. Cyclophosphamide was us ed as a positive control test compound and results were compared to ma nual scoring in Wright-stained slides. In bone marrow, both manual and flow cytometric methods demonstrated positive dose response-trends fo r micronucleated polychromatic erythrocytes (MNPCE). Significant eleva tions in MNPCE were observed at all doses of cyclophosphamide, and com parisons between methods in bone marrow were not statistically differe nt. The flow cytometric method was more sensitive in spleen samples, s howing dose-and time-related increases in micronuclei compared with ma nual scoring. AO proved to be a sensitive discriminator of RNA and DNA , allowing distinct separation of polychromatic erythrocytes (PCE), no rmochromic erythrocytes (NCE), total nucleated cells (TNC), and micron ucleated populations within both PCE and NCE regions. These results su pport the use of AO-based flow cytometry to provide a rapid and sensit ive indicator of micronuclei inducers or non-inducers. (C) 1998 Elsevi er Science B.V. All rights reserved.