Dual effects of molybdenum on mouse oocyte quality and ovarian oxidative stress

Figures & data

Figure 1.  The ovaries exposed to molybdenum (Mo) at 20 mg/L (B) and 40 mg/L (C) exhibited the obvious hyperemia (black arrows), compared to the control group (A) (white arrows).

Figure 2.  Morphological images of M II oocytes (×400). Compared to the control (A), the morphological abnormalities of M II oocytes were observed in mice exposed to molybdenum at ≥20 mg/L, such as no first polar body (B), distorted cytoplasm (C), transformative zona pellucida and excessive vacuolization (D), shrunken cytoplasm (E), and centrally severe granulation (F).

Table 1. Effects of molybdenum exposure on ovary parameters and M II oocyte morphology.

Mo (mg/L)	Ovary index (×10^−3)*	No. ovulation	Abnormal rate/%**
0 (Control)	0.9985 ± 0.0643	31.5000 ± 2.7773	31.8542 ± 2.3361
5	0.9807 ± 0.0511	54.3500 ± 2.8316^a	18.6753 ± 0.8782^a
10	0.9854 ± 0.0527	45.4500 ± 2.6526^a	28.4928 ± 1.9862
20	0.9533 ± 0.0596	41.6000 ± 3.2577^b	34.4304 ± 3.0439
40	0.8394 ± 0.0538^a	35.7368 ± 3.6714	45.4962 ± 3.3147^a

Mo: molybdenum; Data represent means ± SD.

Compared with the control group, ^aP < 0.01, ^bP < 0.05.

*Ovary index = wet ovary weight / total wet body weight; **Abnormal rate = (no. total ovulation - no. normal M II oocytes) / No. total ovulation.

Table 2. Effects of molybdenum exposure on the levels of SOD, GPx, and MDA in ovaries.

Mo (mg/L)	SOD activities (U/mg prot)	GPx activities (U/mg prot)	MDA contents (nM/mg prot)
0 (Control)	115.22 ± 14.32	32.68 ± 1.32	1.0394 ± 0.1282
5	118.56 ± 10.45	36.48 ± 2.03^b	0.9913 ± 0.0113
10	131.38 ± 11.52^b	39.57 ± 3.19^a	0.9756 ± 0.1428
20	100.71 ± 8.78^b	31.39 ± 2.44	1.6071 ± 0.1087^a
40	76.62 ± 6.40^a	22.61 ± 1.73^a	1.6808 ± 0.1886^a

Mo: molybdenum; SOD: superoxide dismutase; GPx: glutathione peroxidise; MDA: malondialdehyde. Data represent means ± SD. Compared with the control group, ^aP < 0.01; ^bP < 0.05.

Figure 3.  Transmission electron microscopic images of the intra-ovarian oocytes (A-C) and the granulosa cells (D-F) in ovaries. Compared to the control (C, F, ×40,000), the mitochondrial vacuolization (A; ×5,000) and the swollen mitochondria with distorted cristae (B; ×40,000) in ovarian oocytes, and the mitochondrial vacuolization in granulosa cells (D, E; ×10,000) were observed in the 20 mg/L (A, D) and 40 mg/L (B, E) group. The arrow indicated the zona pellucida in A, and the arrows or cycle indicated the mitochondria in B-F.