Exposure to Chronic, Low-Dose Rate ÿ-Radiation at Chornobyl Does Not Induce Point Mutations in Big Blue®Mice
Jeffrey K. Wickliffe,1 Amy M. Bickham,1 Brenda E.
Rodgers,1 Ronald K. Chesser,1,2 Carleton J. Phillips,1
Sergey P. Gaschak,2 J.A. Goryanaya,2 I. Chizhevsky,3
and Robert J. Baker1l
1 Department of Biological Sciences, Texas Tech University,
Lubbock, Texas
2International Radioecology Laboratory, Slavutych, Ukraine
3International Chornobyl Center, Kiev, Ukraine
Empirical genetic effects resulting from low-dose point mutations rate
irradiation and chronic, cumulative exposure are poorly characterized.
Expected effects are based on epidemiological studies and downward, linear
extrapolations from nonthreshold models derived from acute, high-dose
exposures. These extrapolations and their associated risk coefficients
have no experimental support, and because of their inherent uncertainty
they are the subject of considerable debate. The expectation of deleterious
genetic effects resulting from low-dose rate irradiation and chronic exposure
is in need of empirical assessment because this type of exposure is typical
of those encountered in occupational, residential, and environmental settings.
Recent acute low-dose « 1 0 cGy) studies using cytogenetic and point
mutation endpoints indicate that observed effects range from those lower
than spontaneous to an increase in the frequency of point mutations. Using
the Big Blue assay®, we examined
the ability of chronic, continuous 'y-irradiation (2.3 X 10-3
cGy/min) in the Chornobyl environment to induce point mutations. This
system has demonstrated a significant point mutation sensitivity (4.5-fold
increase) to acute, high-dose (1-3 Gy) y-radiation. Mutant frequencies
and the muta- tion spectra were examined in exposed and refer- ence samples
of Big Blue® mice following 90 days exposure (cumulative
absorbed dose = 3 Gy) to the Chornobyl environment. No significant increose
in the mutant frequency or bias in the mutational spectrum was observed
in exposed individuals. This finding suggests that low-dose rate y-irradiation
at Chornobyl does not induce point mutations and that cumulative, chronically
absorbed doses do not induce the same genetic effects as acute doses of
the same magnitude. Environ. Mol. Muta- gen. 42: 11-18, 2003.
@ 2003 Wiley-Uss, Inc
Key words: Chornobyl/Chernobyl; Big Blue®;
somatic mutations; transgenic mice; environmental radiation
SREL Reprint #2802
Wickliffe, J. K., A. M. Bickham, B. E. Rodgers, R. K. Chesser, C. J. Phillips, S. P. Gaschak, J. A. Goryanaya, I. Chizhevsky and R. J. Baker. 2003. Exposure to chronic, low-dose rate ¡-Radiation at Chornobyl does not induce point mutations in Big Blue Mice. Environmental and Molecular Mutagenesis 42:11-18.
