Long term effects of ionizing radiation on mouse spermatogenesis.

The effects of acute or split dose exposure to radiation on murine stem cell spermatogonia were analysed. Flow cytometry was applied to estimate the percentages of haploid germ cells (round and elongated spermatids) up to 12 months after irradiation. The recovery in the number of haploid germ cells continued gradually during the period under observation. The intervals between the two equal doses in split dose exposures were 0, 4, 8, 24 and 48 hours. Split doses that were 24 h or 48 h apart had more harmful effects on spermatogenesis than split doses with 4 or 8 hours intervals or acute exposures. The repair capacity of the stem cell spermatogonia was remarkably high.