title: Induction and decline of HPRT mutants and deletions following a low dose radiation exposure at Chernobyl.
abstract: This study was conducted to evaluate the ability of mutation in the hypoxanthine-phosphoribosyltransferase gene (HPRT) to detect radiation-induced mutation in lymphocytes of Russian Chernobyl Clean-up workers, particularly as a function of time after exposure. It is part of a multi-endpoint study comparing HPRT mutation with chromosome translocation and glycophorin A mutation [Radiat. Res. 148 (1997) 463], and extends an earlier report on HPRT [Mutat. Res. 431 (1999) 233] by including data from all 9 years of our study (versus the first 6 years) and analysis of deletion size. Blood samples were collected from 1991 to 1999. HPRT mutant frequency (MF) as determined by the cloning assay was elevated 16% in Clean-up workers (N=300, the entire group minus one outlier) compared to Russian Controls (N=124) when adjusted for age and smoking status (P=0.028). Since exposures occurred over a short relative to the long sampling period, the year of sampling corresponded roughly to the length of time since exposure (correlation coefficient=0.94). When date of blood sample was considered, Control MF was not time dependent. Clean-up worker MF was estimated to be 47% higher than Control MF in 1991 (P=0.004) and to decline 4.4% per year thereafter (P=0.03). A total of 1123 Control mutants and 2799 Clean-up worker mutants were analyzed for deletion type and size by PCR assay for retention of HPRT exons and flanking markers on the X chromosome. There was little difference between the overall deletion spectra of Clean-up workers and Controls. However, there was a decline in the average size of deletions of Clean-up workers as time after exposure at Chernobyl increased from 6 to 13 years (P< or =0.05). The results illustrate the sensitivity of HPRT somatic mutation as a biomarker for populations with low dose radiation exposure, and the dependence of this sensitivity on time elapsed since radiation exposure.
authors.affiliation: Biology and Biotechnology Research Program, Lawrence Livermore National Laboratory, L-441, P.O. Box 808, Livermore, CA 94550, USA.
authors.forename: Cynthia B
authors.initials: CB
authors.lastname: Thomas
authors.forename: David O
authors.initials: DO
authors.lastname: Nelson
authors.forename: Pavel
authors.initials: P
authors.lastname: Pleshanov
authors.forename: Irene M
authors.initials: IM
authors.lastname: Jones
mesh_terms: D000328:Adult; D002999:Clone Cells / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D017353:Gene Deletion; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics* / Q000528:radiation effects*; D008214:Lymphocytes / Q000201:enzymology* / Q000528:radiation effects; D018895:Microsatellite Repeats / Q000235:genetics; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D016273:Occupational Exposure; D016133:Polymerase Chain Reaction; D011210:Power Plants; D018788:Radioactive Hazard Release; D012426:Russia
chemical_list: D004247:DNA; D007041:Hypoxanthine Phosphoribosyltransferase