Increasing environmental contamination with microplastics (MPs) raises significant concerns regarding their potential impact on reproductive health. This study evaluated the effects of prolonged oral exposure to fluorescent polystyrene microplastics (FPS-MPs) of different sizes on the male reproductive system in Wistar rats. Juvenile male rats at 21 days of age were exposed to FPS-MPs of 1 µm and 5 µm for 52 days, covering the period of sexual maturation and a complete spermatogenesis cycle. Body weight, reproductive organ indices, serum levels of testosterone (T), estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), as well as sperm motility and morphology, were assessed. Reproductive potential and accumulation of microplastics in reproductive tissues were also evaluated. No significant differences were observed in body weight or most reproductive organ indices, except for a slight reduction in the left epididymis index in the group exposed to 5 µm particles. FPS-MPs induced size-dependent changes in the hormonal profile, including decreases in T and E2 and compensatory increases in FSH and LH, as well as impairments in sperm quality, which were more pronounced in rats exposed to smaller particles. In conclusion, fertility potential remained preserved, while FPS-MPs accumulated in the testes and epididymides, demonstrating subclinical, size-dependent effects on the male reproductive system.

Microplastics (MPs) represent an increasing environmental and biological concern, with their potential effects on early development and physiological homeostasis still not fully elucidated. The present study aimed to evaluate the effects of chronic juvenile exposure to 1 μm and 5 μm polystyrene microplastics (PS-MPs) on growth, organ indices, and endocrine profile in Wistar rats. A total of 36 juvenile Wistar rats (18 males and 18 females) were orally exposed to PS-MPs (0.1 mg/day) from postnatal day (PND) 21 to PND 61. Body weight dynamics were monitored throughout the experimental period, while at the end of exposure organ indices and serum levels of testosterone and estradiol were assessed. Exposure to PS-MPs was associated with delayed body weight gain, with more pronounced effects observed following exposure to 1 μm particles. Organ-specific and sex-dependent alterations were observed, predominantly affecting brain, lung, and spleen indices, as well as reproductive organs, with effects varying according to both sex and particle size. In addition, significant changes in serum sex hormone levels were detected, characterized by decreased testosterone in males and decreased estradiol in females. In conclusion, juvenile exposure to PS-MPs was associated with sex- and size-dependent alterations in growth dynamics, organ indices, and endocrine status in Wistar rats, suggesting potential systemic physiological effects of microplastics during early development.