Effect of Gamma Radiation on the Prepuberal Bovine Ovary

Abstract

Ninety-five Hereford calves were exposed to either whole-body (dose range 200 to 400 R, 60Co, 0. 7 R/min) or localized (dose range 300 to 1200 R, 137Cs, 75 R/min) doses of gamma-radiation. Forty-three animals served as controls. Ovaries were excised either surgically or at sacrifice at postirradiation intervals of 30 to 700 days and analyzed microscopically for radiation effects. At 30 to 150 days postirradiation, doses of 600 R or less (local or whole-body) resulted in minor increases in atresia of primordial follicles and elevated numbers of growing and vesicular follicles. The superfollicular response was generally heightened with increasing dose. Follicular quality, however, declined as follicular quantity increased. At 700 days after the 200-R whole-body exposure, 98% of the primordial follicles (versus 78% for controls) showed degenerative changes, and evidence of the superfollicular response was lost. Suppression of follicular growth was severe following 900 R and was all but complete with 1200 R. Primordial follicle survival after 900 R was 42% of control, and 17% survived 1200 R to 500 days postirradiation. Following exposures of 300 R or greater, all but 4 of 12 animals developed to 500 days post-irradiation experienced first estrus within expected age limits. Corpora lutea present at slaughter were, in all cases, abnormal.