Radiation Sensitivity of Oöcytes at Different Stages of Development in the Immature Mouse

Abstract

A single dose of 20 r X-irradiation to neonatal and immature mice of different ages has an effect on the ovary which can be correlated with the developmental stages of the oocytes. Radiation on the day of birth destroys 50% of the small oocytes in the newborn ovary, whereas the same dose to a 7-day-old mouse leaves only 5% of the small ova intact. Radiation at 2 and 3 weeks of age causes 98% to 99% immediate cell death among the small ova. This variation in radiation response corresponds to the distribution of the different oocyte stages in the ovary at the time of radiation. Oocytes in pachytene and late diplotene are highly sensitive to 20 r of radiation whereas nuclei in early diplotene and dictyotene show no immediate damage at this dose level.