Effect of Subchronic Oral Exposure to Polystyrene Microplastics on Female Rats

Microplastics (MPs) are increasingly recognized as environmental contaminants with potential impacts on reproductive health. The current study investigated the effects of oral exposure to polystyrene MPs of different sizes for 30-days on the hormonal and ovarian oxidative profile of female Wistar rats. After the 30-day exposure to 1 µm particles, the results showed elevated estradiol (4.51±0.17 ng/dL) and testosterone levels (3.73±0.68 ng/dL) compared to the control group (4.35±0.16 ng/dL and 3.40±0.20 ng/dL, respectively) and the 5 µm particles group (4.33±0.23 ng/dL and 3.43±0.40 ng/dL). Follicle-stimulating hormone decreased in the 1 µm group (2.23±0.77 ng/dL) relative to the control (2.60±1.15 ng/dL) and 5 µm (2.70±1.55 ng/dL), while luteinizing hormone increased in the 5 µm group (3.73±0.55 ng/dL) compared to the control (2.03±1.53 ng/dL) and 1 µm (2.10±1.03 ng/dL). Regarding the oxidative status, lipid peroxidation was significantly higher in the 1 µm group (0.25±0.07 nmol MDA/mg protein) than in the control (0.16±0.03; P≤0.01) and 5 µm group (0.17±0.02 nmol MDA/mg protein). Compared to the control (157.14±52.13 ng/mg protein) total glutathione increased in both experimental groups (234.52±54.53 ng/mg protein; P≤0.05 for the 1 µm group and 304.70±57.75 ng/mg protein; P≤0.001 for the 5 µm group). These findings suggest that particle size can play a critical role in modulating hormonal and oxidative responses, highlighting potential reproductive risks associated with MPs exposure which poses threats to biodiversity reducing population viability.