Alteration of mouse oocyte quality after a subchronic exposure to depleted Uranium

Gametes and embryo tissues are known to represent a sensitive target to environmental toxicants exposure. Oocyte quality can impact subsequent developmental competence, pregnancy course and even adult health. The major health concern from depleted uranium (DU) is mainly centred on its chemotoxic properties as a heavy metal. Little attention was paid to the impact of uranium on female gamete quality. The aim of this research was to evaluate the effect of DU on mouse oocyte quality after 49 days of subchronic contamination in drinking water and to correlate the observed effects with the amount of DU accumulated in organs. Four different DU concentrations were investigated: 0 (control), 10 (DU10), 20 (DU20) and 40 mg L−1 (DU40). DU did not influence the intensity of ovulation but affected oocyte quality. The proportion of healthy oocytes was reduced by half (P < 0.001) from 20 mg L−1 compared with control group (0.537; 0.497; 0.282 and 0.239 in control, DU10, DU20 and DU40 groups respectively) whereas no accumulation of DU was recorded in the ovaries whatever the dose tested. Abnormal perivitelline space (P < 0.001) or absence of the 1st polar body (P < 0.001) was identified as the main characteristic of DU impact. In the context of this study, the NOAEL for oocyte quality was determined at 10 mg L−1 in drinking water (1.9 mg kg−1 day−1). An increase in the dose of contamination over 20 mg L−1 did not amplify the proportion of oocytes contracting a specific alteration but conducted to a diversification in oocytes abnormalities. Further investigations are necessary to correlate morphologic assessment of female gamete with its developmental competence.