title: The measurement of DNA strand breaks in rat colonic mucosa by fluorometric analysis of DNA unwinding.
abstract: We describe the detection of DNA strand breaks in the rat colonic mucosa (in vivo and in vitro) by fluorometric analysis of DNA unwinding. DNA strand breaks were detected, in a dose-dependent manner, 2 h following an intracaecal dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 5-100 mg/kg). Levels of double-stranded DNA in the colonic mucosa of control animals, after 60 min unwinding time, were 62.8 +/- 3.4% (n = 6) and were significantly reduced at 5 mg/kg to 52.1 +/- 1.9% (n = 3). DNA strand breaks were also detected in isolated rat colonic mucosal cells following 15 min treatment with MNNG (0.1-1 mM) in vitro. The percentage of double-stranded DNA, after 60 min unwinding time, was significantly reduced (13.6 +/- 5.4%, n = 3) from control levels following treatment with 0.1 mM. A post-treatment incubation (30 min) of cells treated at a MNNG concentration of 0.25 mM resulted in 78.2 +/- 24.0% (n = 3) of these lesions being repaired.
authors.affiliation: School of Biochemistry, University of Birmingham, U.K.
authors.forename: A J
authors.initials: AJ
authors.lastname: Percy
authors.forename: J K
authors.initials: JK
authors.lastname: Chipman
mesh_terms: D000818:Animals; D003106:Colon / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D005470:Fluorometry / Q000379:methods; D007413:Intestinal Mucosa / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000008:administration & dosage / Q000633:toxicity; D009690:Nucleic Acid Conformation / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008769:Methylnitronitrosoguanidine