Effects of X-ray irradiation on genomic DNA methylation levels in mouse tissues

Effects of ionizing radiation on the level of genomic DNA methylation in Li ver, brain and spleen of mouse as well as in two kinds of cultured cells we re examined by high-performance liquid chromatography. Ten Gy of whole body X-radiation reduced the 5-methyldeoxycytidine contents by about 40% within 8 hours after irradiation in liver. Similar effects were observed at 4 or 7 Gy of X-ray irradiation. However, no such change was detected in brain, s pleen and cultured cells. The data indicate that radiation-induced alterati on in genomic DNA methylation is not ubiquitous among different tissues and cells.