title: Dose-rate effect on the induction of HPRT mutants in human G0 lymphocytes exposed in vitro to gamma radiation.
abstract: The influence of dose rate on expression time, cell survival and mutant frequency at the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus was evaluated in human G(0) peripheral blood lymphocytes exposed in vitro to gamma rays at low (0.0014 Gy/min) and high (0.85 Gy/min) dose rates. A cloning assay performed on different days of postirradiation incubation indicated an 8-day maximum expression period for the induction of HPRT mutants at both high and low dose rates. Cell survival increased markedly with decreasing dose rate, yielding D(0) values of 3.04 Gy and 1.3 Gy at low and high dose rates, respectively. The D(0) of 3.04 Gy obtained at low dose rate could be attributed to the repair of sublethal DNA damage taking place during prolonged exposure to low-LET radiation. Regression analysis of the mutant frequency yielded slopes of 12.35 x 10(-6) and 3.66 x 10(-6) mutants per gray at high and low dose rate, respectively. A dose and dose-rate effectiveness factor of 3.4 indicated a marked dose-rate effect on the induced HPRT mutant frequency. The results indicate that information obtained from in vitro measurements of dose-rate effects in human G(0) lymphocytes may be a useful parameter for risk estimation in radiation protection.
authors.affiliation: Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102, Tamilnadu, India.
authors.forename: P R Vivek
authors.initials: PR
authors.lastname: Kumar
authors.forename: Mary N
authors.initials: MN
authors.lastname: Mohankumar
authors.forename: V Zareena
authors.initials: VZ
authors.lastname: Hamza
authors.forename: R K
authors.initials: RK
authors.lastname: Jeevanram
mesh_terms: D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D004781:Environmental Exposure / Q000009:adverse effects*; D005720:Gamma Rays / Q000009:adverse effects*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics* / Q000378:metabolism*; D008214:Lymphocytes / Q000166:cytology / Q000201:enzymology* / Q000528:radiation effects*; D009154:Mutation; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D016192:Resting Phase, Cell Cycle / Q000502:physiology / Q000528:radiation effects; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase