Background Soy isoflavone has similar structure and function to endogenous estrogen and is widely found in soy products. Previous studies have shown that soy isoflavone exposure at different developmental stages has different effects on female reproductve system, but there are no relevant reports on adult soy isoflavone exposure.
Objectve This animal experiment explores the effects of adulthood soy isoflavone exposure on ovarian follicle development in rats, aiming to provide a scientfc basis for the ratonal use of soy isoflavone in adulthood.
Methods Forty-four three-month-old clean female Wistar rats were randomly divided into control group, and low-, medium-, and high-dose soy isoflavone groups (25, 50, and 100 mg/kg), 11 rats per group, and received intragastric administraton once a day for six months. Afer that, the ovary was weighed and organ coefcient was calculated; the histological changes of ovary were observed and the follicle proporton was calculated; the ant-Muller hormone (AMH) level in serum was determined; the mRNA expression levels of AMH, estrogen receptor β (ERβ), oocyte-specifc linker histone (H1foo), stem cell factor (SCF), and its receptor (c-Kit) in ovary were determined.
Results Compared with the control group, there was no signifcant difference in body weight, ovary weight, and its organ coefcient in the three dose groups (P>0.05). Compared with the control group, the proporton of pre-antral follicles in the low-dose group was increased (12.2% vs 8.6%); the proporton of antral follicles was increased (40.7% vs 30.3%), but the proporton of corpus luteum was decreased (7.4% vs 19.1%) in the middle-dose group; the proportion of pre-antral follicles was decreased (3.4% vs 8.6%), while the proporton of atresia follicles was increased (53.8% vs 42.0%) in the high-dose group; all the differences were statstcally signifcant (P < 0.05). There was no signifcant difference in serum AMH levels (P>0.05) across all groups, but the expression levels of AMH mRNA were decreased in the low-and medium-dose groups and increased in the high-dose group (control:1.00±0.03; low-dose:0.58±0.03; mediumdose:0.53±0.03; high-dose:2.82±0.37; P < 0.05). Compared with the control group (0.92±0.07), the expression levels of c-Kit mRNA were up-regulated in the low-, medium-, and high-dose groups (1.19±0.01, 1.50±0.07, and 1.80±0.15, respectvely, P < 0.05), and the level of SCF mRNA in the low-dose group and the levels of H1foo and ERβ mRNA in the high-dose group were also up-regulated(2.08±0.06) vs (1.19±0.29), (1.46±0.03) vs (1.03±0.13), and (1.29±0.26) vs (0.92±0.09), respectvely, P < 0.05.
Conclusion Exposure to soy isoflavone at 25 mg/kg and above in adult rats could affect ovarian follicle development through affectng the expression of ovarian cytokines.
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