Premature menopause and obesity due to oocyte loss in female mice chronically exposed to low dose-rate γ-rays

In previous reports, the authors showed a significant overall increase in neoplasms originating from the ovaries (2007) and increased body weights (2007, 2010) in female B6C3F1 mice chronically exposed to low dose-rate γ-rays at 20 mGy/day (total doses = 8 (2007) or 6 Gy (2010)), as well as significant increases in serum leptin, total cholesterol, adipose tissue deposits and liver lipid content (2010). The present study chronicles the progression of ovarian failure in relation to obesity and dyslipidemia in female B6C3F1 mice chronically exposed to low dose-rate of γ-rays from 9 to 43 weeks of age (total dose = 4.8 Gy). We monitored changes in body weights, estrus cycles, ovarian follicle counts, serum cholesterol and serum leptin. The number of mice with irregular estrus cycles and increased body weights (with increased fat deposits) significantly increased from 30-36 weeks of age. Depletion of oocytes in ovaries from irradiated mice at 30 weeks of age (accumulated dose = 3 Gy) was also observed. Findings suggest that obesity in female B6C3F1 mice continuously irradiated with low dose-rate of γ-rays at 20 mGy/day is a consequence of premature menopause due to radiation-induced oocyte depletion. (authors)