Low persistence of radiation-induced centromere positive and negative micronuclei in cultured human cells

The micronucleus (MN) assay is widely used both in genetic toxicology and i n the biomonitoring of human populations. Lymphocytes, cell lines, and bone marrow and epithelial cells are usually employed as target systems in such studies. However, little effort has been done to assess the persistence of MN in highly proliferative cells. To study the behaviour of MN containing whole chromosomes or acentric fragments, we have performed a time course ex periment on the persistence of gamma-ray (3 Gy) induced MN in a human lymph oblastoid cell line. The frequency and content of MN were analyzed 1, 3, 7, 14, and 56 days after irradiation by pancentromeric fluorescence in situ h ybridization (FISH). We observed a clear induction of both centromere posit ive and negative MN at completion of the first mitotic division. The freque ncy of both types of MN drastically declined to basal levels 7 days after i rradiation with an identical kinetics. We therefore conclude that centromer e positive and negative MN are highly unstable upon cell division, indicati ng that the MN assay could not be a good biomarker of DNA damage induced by acute treatments in highly proliferative cells. The implication of our fin dings in biomonitoring and in genotoxicity studies is discussed. (C) 1999 E lsevier Science B.V. All rights reserved.