title: Sister chromatid exchange induction and the course of DNA duplication, two mechanisms of sister chromatid exchange induction by ENU and the role of BrdU.
abstract: The aims of the present study were to establish the following: (i) the course of sister chromatid exchange (SCE) induction by ethylnitrosourea (ENU) in the first, second and third divisions as a function of the exposure time; (ii) the persistence of SCE-inducing lesions and the determination of whether or not they are always involved in SCE formation; (iii) the effect of bromodeoxyuridine (BrdU) incorporation on the induction and persistence of SCE. Three-way differential staining of sister chromatids in murine bone marrow cells in vivo was used in the present study. The results indicate the following: (i) SCE induction in each cell division depends on the course of DNA duplication, suggesting that SCE occurs at the replication fork; (ii) the cell population under study could be considered synchronous and had a cell cycle duration of nearly 9 h; (iii) in the second and third cell divisions ENU preferentially induced SCE in the cycle in which the exposure occurred; (iv) lesions induced by exposure to ENU did not cause SCE at the same site in subsequent divisions; (v) ENU was also capable of producing a long-lasting induction of SCE in BrdU-unsubstituted DNA; (vi) the sensitivity to SCE induction by the mutagen increases nearly proportionally to BrdU incorporation into DNA.
authors.affiliation: Departamento de Genética, Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027, México, D.F. Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Rodríguez-Reyes
authors.forename: P
authors.initials: P
authors.lastname: Morales-Ramírez
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000648:ultrastructure; D001973:Bromodeoxyuridine / Q000737:chemistry / Q000494:pharmacology*; D002453:Cell Cycle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects / Q000648:ultrastructure; D002842:Chromatids / Q000187:drug effects / Q000648:ultrastructure; D004247:DNA / Q000737:chemistry / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005038:Ethylnitrosourea / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009153:Mutagens / Q000494:pharmacology*; D051381:Rats; D012854:Sister Chromatid Exchange / Q000187:drug effects*
chemical_list: D009153:Mutagens; D004247:DNA; D001973:Bromodeoxyuridine; D005038:Ethylnitrosourea