"Low Level
Radiation Health Effects: Compiling  the Data"

Revision 2
March 19, 1999

by Radiation, Science, and Health, Inc.,
Edited by J. Muckerheide

1.3
Animal & Plant
Biology

1.3.1
Mammals

References

"Average numbers of ovulations, implantations, and living fetuses obtained from rats x-irradiated during the estrous cycle before mating are a function of both the radiation dose and the time of exposure during the cycle. Animals irradiated during metestrus or the day thereafter exhibit significant increases in the factors studied, while those irradiated on the 3rd day after metestrus maintain fewer implantations after exposure to 300, 500, and 600 roentgens, and fewer living fetuses after exposure to 100 to 600 roentgens."

"A total of 512 virgin female rats (Sprague-Dawley), weighing 175 to 190 g, were subjected to whole-body exposures of 50- to 600-r x-rays on the day of metestrus (M) or 1, 2, or 3 days after metestrus (M+l, M+2, M+3)."

"There was no discernible increase in abnormally developed fetuses in irradiated females. Also the incidence of fetal death was extremely low during the latter trimester of pregnancy. In females irradiated on the day of metestrus there was, like ovulations and implantations, a significant increase in the number of living fetuses following 100 to 600 r (Fig. 1).

                                 Figure 1

The response paralleled the linear increase in implantations, reaching a maximum of 15.5 fetuses per female after 500 r, then declining to 13.0 per female after 600 r. Females irradiated on the day after metestrus responded with significantly more living fetuses following doses of 200 to 500 r. The maximum responses were observed after 200 and 300 r, followed by a slight decline after 400 and 500 r and a significant decrease to 7.7 fetuses after 600 r. Number of fetuses in females irradiated on the 2nd day after metestrus remained at control levels for all doses except 600 r when the number was significantly reduced to an average of 5.4 fetuses. Average number of fetuses found in females irradiated on the 3rd day after metestrus decreased in a linear fashion from 100 to 600 r with a range of 5.8 after 100 r to 0.9 after 600 r."

"Exposure to 50 r had no effect on the reproductive factors studied, regardless of the time of exposure."