Objective To study the time-and dose-effect of mitochondrial DNA (mtDNA) 4934 bp and 4977 bp deletions in the human peripheral blood irradiated by137 Cs γ-rays,and to evaluate its implication in biological dosimetry.Methods The peripheral blood from five healthy adults was collected and irradiated with γ-rays.The peripheral blood of one healthy adult was irradiated with 5 Gy and cultured for 2,24,48 and 72 h after irradiation.The peripheral blood from the other four healthy adults was cultured for 2 h after 0,0.5,1,2,5 and 10 Gy irradiation.The peripheral blood mtDNA 4934 bp and 4977 bp deletions were detected by real-time polymerase chain reaction and gel electrophoresis.The doseeffect curves were fitted using Curve Expert 1.4 Software.Results mtDNA 4934 bp and 4977 bp deletions were induced at 2 h post-irradiation and the mtDNA 4934 bp deletion had relative high levels at 2 h and 48h after radiation (t =10.782 and 8.966,P ＜ 0.05),and mtDNA 4977 bp deletion reached the highest level at 48 h after radiation (t =7.433,P ＜0.05).mtDNA 4934 bp (t =2.895-8.105,P ＜0.05) and 4977 bp deletion (t =3.006-7.715,P ＜0.05) irradiated at 0.5-10 Gy increased with a dosedependent manner.The incidence of mtDNA 4977 bp deletion was higher than that of 4934 bp deletion for those samples exposed with same dose of irradiation,especially at 10 Gy (t =2.919,P ＜ 0.05),which suggested that 4977 bp deletion might be more sensitive than 4934 bp deletion at high dose.But larger individual differences were found in 4977 bp deletion compared with 4934 bp deletion.The dose-effect equations for 4934 bp deletion and 4977 bp deletion were Y1 =1.178 + 0.1219D (R2 =0.9269) and Y2 =1.2578 +0.1933D (R2 =0.9016),respectively.Conclusions The induction of mtDNA deletion was correlated with radiation dose,and thus it may be a available method for biological dose estimation and prognostic evaluation.

Objective To explore the feasibility of using glycophorin A somatic mutation in peripheral erythrocytes,in order to evaluate the cancer risk of occupational medical exposure to ionizing radiation.Methods Totally 336 medical radiation workers were recruited as three groups (general radiation group,computer tomography group,intervention and radiation treatment group) and 112 healthy adults were selected as control by using stratified random cluster sampling method,where 176 medicalradiation workers and 58 health controls had a MN-heterozygous type.The erythrocytes were fixed and bound with fluorescent-labeled monoclonal antibody,and the glycophorin A somatic mutation frequency was assayed by a modified BR6-1W1 method using a FACScan flow cytometer.The individual susceptibility to radiation was investigated using micronuclei test and 3-Aminobenzamide index test.Results The GPA somatic mutation frequency of medical-radiation workers was significantly higher than that of healthy control ( t =2.29 - 11.48,P ＜ 0.05 ).In particular,the NO GPA aberration frequency of interventional radiology workers was much higher than that of the general medical diagnostic workers (t =2.01,P ＜ 0.05).In addition,the NO GPA variant frequency changed significantly with the years of radiation service,cumulative doses,and 3AB index.However,the NN GPA variant frequency was only associated with the years of radiation service,and no significant correlations were found between NN GPA variant frequency and cumulative dose of radiation exposure or 3AB index. Conclusions GPA mutation frequency,especially NO GPA mutation frequency could be used as a sensitive biomarker to predict the DNA damage and individual susceptibility for the population exposed to professional low-dose ionizing radiation.