Increased levels of comet-detected spermatozoa DNA damage following in vivo isotopic- or X-irradiation of spermatogonia

To investigate whether DNA damage arising in spermatogenic germ cells can b e detected in resultant sperm, we have irradiated murine testis and collect ed spermatozoa from the vas deferens 45 days later. These cells were derive d from spermatogonia present at the time of irradiation. Two forms of irrad iation were used, external X-rays (4 Gy) and internal auger electrons from contamination of the male mouse with the isotope Indium-114m (1.85 MBq), wh ich was localised in the testis. Both forms of irradiation produced a profo und fall in vas deferens sperm count and testis weight, Indium-114m being m ore effective. Using the neutral Comet assay for double strand break detect ion, significant increases in sperm comet tail length and moment were obser ved. The levels of damage were similar for both treatments. Care had to be taken during the assay to distinguish between sperm and somatic cells as th e proportion of the latter increased after irradiation. We conclude that th e comet assay can detect DNA damage in spermatozoa after the in vivo exposu re of male germ cells to a known testicular genotoxic agent. The assay may be useful for the assessment of sperm DNA damage (double stranded) associat ed with male infertility and post-fertilization developmental abnormalities in the offspring. (C) 2001 Elsevier Science B.V. All rights reserved.