Somatic cell mutations at the glycophorin a locus in erythrocytes of radiation workers from the Sellafield nuclear facility.

The glycophorin A (GPA) somatic mutation assay for N0 and NN mutant erythrocytes was performed on 245 current and 48 retired workers who had been occupationally exposed to radiation at the British Nuclear Fuels plc facility at Sellafield. A positive association with increasing age was found for current workers for both N0 and NN frequencies of 0.14 +/- 0.05 x 10(-6) (P = 0.012) and 0.25 +/- 0.07 x 10(-6) (P = 0.0003) per year, respectively. No association with age was found for the retired workers. In a comparison of ever-smokers with never-smokers, no difference was observed for N0 frequencies for current workers, but a significantly higher frequency was found for ever-smokers in the retired group (P = 0.001). NN mutant frequencies were slightly higher in ever-smokers than in never-smokers for both current and retired workers, but in neither case was the increase significant. In age-adjusted analyses for N0 mutant frequencies, a slight positive radiation dose response was found for current workers (1.6 +/- 3.8 x 10(-6) per Sv), for retired workers (2.9 +/- 2.5 x 10(-6) per Sv), and in the combined analysis (2.6 +/- 2.2 x 10(-6) per Sv), but in no case did this reach significance. Similar analyses for NN mutant frequencies revealed a positive dose response for current workers (4.7 +/- 4.6 x 10(-6) per Sv) and a negative response for retired workers (-2.4 +/- 3.6 x 10(-6) per Sv) that was maintained in the combined analysis (-1.4 +/- 2.8 x 10(-6) per Sv), but none of these slopes was significantly different from zero. The results suggest that the GPA mutation assay is insufficiently sensitive to be used as a biological marker of low-dose chronic exposure and provide further evidence that, in contrast to high acute radiation exposure, protracted exposure is much less effective at inducing somatic mutations in vivo.

[Long-term effects of chronic radiation exposure on the level of somatic mutations in peripheral blood cells]. / Vliianie khronicheskogo radiatsionnogo vozdeistviia na uroven' somaticheskikh mutatsii v kletkakh perifericheskoi krovi liud ei v otdalennye sroki.

The level of comatic mutations was studied at GPA locus and in the TCR system at late times since the onset of radiation exposure in persons exposed to chronic radiation accidents at the Mayak Production Association in the period 1949-1952. Individuals with predominantly external gamma-exposure and those with predominantly internal (mainly due to 90Sr) exposures have been identified among the exposed population. The average dose to red bone marrow made up 121.5 cSv with individual values ranging from 11.0 to 462.7 cSv. An increased frequency of TCR-mutant lymphocytes was noted for exposed subjects. The level of GPA-variant erythrocytes of different types in the study group did not differ from the respective value registered in control. The analysis of TCR status showed no dependence of mutant cell frequency on exposure dose. The assumption is made that the rate of exposure dose and the nature of its formation (chronic exposure) exert a decisive influence on the level of somatic mutations in peripheral blood cells in humans.

Determination of somatic mutant frequencies at glycophorin A and T-cell receptor loci for biodosimetry of prolonged irradiation.

PURPOSE: To determine the variant frequencies (VF) at glycophorin A (GPA) and T-cell receptor (TCR) loci in persons exposed to prolonged ionizing radiation at different doses and to assess the significance of the GPA and TCR assays for biodosimetry of prolonged irradiation. MATERIALS AND METHODS: The VF values were determined by means of flow cytometry in 120 persons exposed between 1968-1996. Most exposures were in Chernobyl clean-up workers in 1986-1987. RESULTS: A significant correlation was shown between the NO GPA variant cell frequency and dose (r = 0.61, p < 0.0001). The slope of the linear regression was 6.3 x 10(-6) NO mutant cells/Gy. Dose-dependent increase in the TCR VF was found in the group with recent exposures (slope 2.1 x 10(-4) variant cells/Gy, r = 0.75, p = 0.0002). In the Chernobyl clean up workers who received doses less than 0.25 Gy the TCR VF unlike the GPA VF was significantly higher than in the control non-irradiated individuals (p < 0.01 and p > 0.05 respectively). CONCLUSIONS: The GPA assay has limited potential to be used as a biodosimeter of prolonged irradiation, at least in dose interval up to 2.0 Gy. The TCR assay is likely to have greater potential in estimation of recent radiation exposure than the GPA assay.

[The estimation of the level of mutations at the glycophorin A locus in subjects exposed to the chronic action of ionizing radiation]. / Otsenka urovnia mutatsii v lokuse glikoforina A u lits, podvergavshikhsia khronicheskomu vozdeistviiu ioniziruiushchei radiatsii.

11 persons, who had been irradiated chronically at low dose rate under occupational conditions in 1950s in doses 220-581 cGy according data of individual film dosimeters, and 5 control persons were examined regarding the level of glycophorin A (GPA) mutation type NO and NN in blood erythrocytes. Significantly higher level of GPA mutations type NO was registered in average in the group of exposed persons (23.2 +/- 4.6 x 10(-6)) compared with the control group (10.2 +/- 2.1 x 10(-6)) through the dose dependence was expressed slightly. The coefficient of the linear regression has equaled (2.3 +/- 1.2 x 10(-6)) Gy. The outlook on GPA assay usage in retrospective biodosimetry is discussed.

[Determination of mutation frequency at loci of glycophorin A and T-cell receptors: informativeness for biological dosimetry of acute and prolonged irradiation]. / Opredelenie chastoty mutatsii po lokusam glikoforina A i T-kletochnogo retseptora: informativnost' dlia biologicheskoi dozimetrii ostrogo i prolongirovannogo oblucheniia.

The frequencies of somatic mutations at loci of glycophorin A (GPA) and T-cell receptor (TCR) were determined in persons exposed professionally to ionizing radiation or a result of accidents at nuclear power plants and in control donors. Dependence of glycophorin A mutant (NO) cell frequency on doses of acute (up to 3.5 Gy) and prolonged (up to 15.0 Gy) irradiation was shown. The slope of linear regression corresponded to increase of NO-mutant frequency by 31.1 x 10(-6)/Gy (r = 0.87, p < 0.0001) for acute irradiation and by 6.3 x 10(-6)/Gy (r = 0.61, p < 0.0001) for prolonged one. The 5-fold decrease of the linear regression slope in the case of prolonged irradiation makes significantly worse permissive ability of the GPA test. Therefore its use for biological dosimetry of prolonged irradiation is not expedient in dose interval up to 1 Gy. The frequency of mutations in genes of T-cell receptor significantly correlated with dose of irradiation only in group of donors with recent radiation exposure (r = 0.75, p = 0.0002). Meanwhile, the TCR method is more sensitive and informative for biological dosimetry of recent radiation, than the GPA test.

[Determination of mutation frequency at loci of glycophorin A and T-cell receptor: study of Chernobyl AES accident cleanup workers]. / Opredelenie chastoty mutatsii po lokusam glikoforina A i T-kletochnogo retseptora: obsledovanie likvidatorov avarii na CHAES.

The frequencies of somatic mutations at loci of glycophorin A (GPA) and T-cell receptor (TCR) were determined in control unexposed donors and Chernobyl clean up workers, who received low doses of irradiation up to 0.25 Gy. High variability of mutant rates for two investigated genes was shown in the clean up workers. No significant difference in the GPA (NO) mutant frequencies was observed between the clean up workers and control donors (p > 0.05), though there is a tendency for increasing the GPA mutation rate in the clean up workers. Meanwhile, the TCR mutation rate was significantly increased the clean up workers (p < 0.01), perhaps because of acceleration of spontaneous mutagenesis and possible genome instability. Persons with elevated levels of mutations at two loci can present a group at high risk in respect to oncological diseases.

Glycophorin A somatic cell mutation frequencies in residents of Tibet at high altitudes.

Since cosmic radiation is absorbed by the atmosphere surrounding the Earth, people who live at high altitude receive significantly larger amounts of cosmic radiation exposure than do those who live at low altitude. The glycophorin A-based somatic mutation assay was performed on 36 blood samples from two populations of Tibet inhabitants to determine whether residents at high altitude (4,300 m) accumulate more somatic mutations than do those who live at low altitude (1,500-1,900 m). These two populations differ in estimated cumulative lifetime cosmic radiation dose, with high altitude residents having received a mean of 111 mSv while low altitude residents received a mean of 27 mSv. Results showed no significant difference in peripheral blood variant erythrocyte frequency between these two populations and no difference from results of a previous study on Finnish workers who live at very low altitude (<500 m).

Somatic mutations at the glycophorin A (GPA) locus measured in red cells of Chernobyl liquidators who immigrated to Israel.

Glycophorin A (GPA) assays for human erythrocytes with gene expression loss and duplication phenotypes (NO, NN) were carried out on 15 Chernobyl clean-up workers (liquidators) who immigrated to Israel within the preceding 5 years, 19 local Israeli controls, and 14 Russian (nonliquidator) immigrants. GPA phenotype variants in red blood cells of the 15 liquidators showed values ranging from 1 to 101 events/10(6) cells, with a mean +/- SD of 25.6 +/- 7.0. In comparison, the 19 Israeli controls had values ranging from 0 to 13 GPA events per 10(6) cells, with a mean +/- SD of 3.9 +/- 0.8. The difference was highly significant (p < 0.001). Another group of 14 volunteer control subjects (nonliquidators) who had emigrated from the former Soviet Union to Israel during the past 5 years showed values ranging from 0.0 to 35.0 events per 10(6) cells, with a mean +/- SD of 6.1 +/- 2.7. The difference between this group and the liquidator group was significant at p < 0.01. The results are compatible with past exposure to radiation in the group identified as liquidators.

Mutation rates at the glycophorin A and HPRT loci in uranium miners exposed to radon progeny.

OBJECTIVES: To find whether a relation exists between estimated levels of exposure to radon and its progeny and mutations in hypoxanthine phosphoribosyl transferase (HPRT) and glycophorin A in a cohort of former uranium miners. METHODS: A cohort study involving a sample of miners from the Radium Hill uranium mine in South Australia, which operated from 1952 to 1961. Radiation exposures underground at Radium Hill were estimated from historical radon gas measures with a job exposure matrix. Workers from the mine who worked exclusively above ground according to mine records were selected as controls. In 1991-2 miners were interviewed and blood taken for measurement of somatic mutations. Mutation rates for HPRT and glycophorin A were estimated with standard assay techniques. RESULTS: Homozygous mutations of glycophorin A were increased in underground miners (P = 0.0027) and the mutation rate tended to rise with increasing exposure with the exception of the highest exposure (> 10 working level months). However, there was no association between place of work and either the hemizygous mutations of glycophorin A or the HPRT mutation. CONCLUSIONS: There may be an association between glycophorin A mutations and previous occupational exposure to ionising radiation. However, not enough is known at present to use these assays as biomarkers for historical exposure in underground mining cohorts.

Monitoring exposure to atomic bomb radiation by somatic mutation.

Atomic bomb survivors are a population suitable for studying the relationship between somatic mutation and cancer risk because their exposure doses are relatively well known and their dose responses in terms of cancer risk have also been thoroughly studied. An analysis has been made of erythrocyte glycophorin A (GPA) gene mutations in 1,226 atomic bomb survivors in Hiroshima and Nagasaki. The GPA mutation frequency (Mf) increased slightly but significantly with age at the time of measurement and with the number of cigarettes smoked. After adjustment for the effect of smoking, the Mf was significantly higher in males than in females and higher in Hiroshima than in Nagasaki. All of these characteristics of the background GPA Mf were in accord with those of solid tumor incidence obtained from an earlier epidemiological study of A-bomb survivors. Analysis of the dose effect on Mf revealed the doubling dose to be about 1.20 Sv and the minimum dose for detection of a significant increase to be about 0.24 Sv. No significant dose effect for difference in sex, city, or age at the time of bombing was observed. Interestingly, the doubling dose for the GPA Mf approximated that for solid cancer incidence (1.59 Sv). And the minimum dose for detection was not inconsistent with the data for solid cancer incidence. The dose effect was significantly higher in those diagnosed with cancer before or after measurement than in those without a history of cancer. These findings are consistent with the hypothesis that somatic mutations are the main cause of excess cancer risk from radiation exposure.

New approaches for biological monitoring of radiation workers.

Methods for measuring somatic mutation and chromosome aberration in humans are currently advancing and provide important new opportunities for biologic dosimetry of nuclear workers. Methods to test somatic mutation in four human genes (hprt, hla-a, glycophorin A, and beta globin) are reviewed briefly and evaluated for their applicability to biological radiation dosimetry of nuclear workers. Two somatic mutation tests can be currently recommended: an HPRT method applied to recently exposed workers and the glycophorin A method applied to workers exposed over their working lifetime. A new method of chromosome analysis using DNA hybridization with chromosome-specific gene libraries allows one to paint single or multiple chromosome pairs in standard metaphase preparations. This method is ideal for rapid and reliable detection of reciprocal translocations, the key lesion for the evaluation of long-term radiation exposure. Both mutational and aberrational approaches should be fostered in the expectation that they will complement other forms of dosimetry and will improve our ability to clarify whether or not significant health effects are dosimetrically related.