The Effects of Acute X-irradiation on Primordial Germ-cells in the Female Rat

Abstract

Pregnant rats were subjected to 100 r acuteX-irradiationatl0.5days post coitum (p.c). The numbers of oogonia and oocytes present in the ovaries of fetuses aged 15.5-18.5 dyas were then estimated by a volumetric method. Five days after exposure tne total population of germ-cells in irradiated specimens (circa 8000) was reduced to about a third of that in the controls. By 18.5 days, however, the number had risen to 39000, which is just more than 50 percent of the normal complement of germ-cells at that period of foetal development. It has previously been shown that, in contrast to primordial germ-cells, oogonia subjected to 100 r at 15.5 days p.c. succumb to delayed effects of irradiation and thus fail to undergo "regeneration". It may therefore be concluded that the radiation response of female "stem-cells" varies according to their stage of development at the time of exposure.