EFFECTS OF INTRAEPIDIDYMAL INJECTION OF EUGENOL, MAGNETITE NANOPARTICLES, AND THEIR CONJUGATE ON SPERM PARAMETERS AND TESTOSTERONE LEVELS IN WISTAR RATS

Resumo

INTRODUCTION: The search for safe, effective, low-cost alternatives to surgical castration has intensified in the context of population control of stray animals. Intraepididymal injection of chemical agents stands out as a promising strategy to induce male infertility. Eugenol is a phenolic compound with benefic biological properties and also reproductive toxicity relying upon the concentration. It can be conjugated to magnetite nanoparticles (Fe₃O₄), forming eugenol·Fe₃O₄, enhancing its retention and bioavailability in tissues. OBJECTIVE: To evaluate the effects of a single intraepididymal injection of eugenol, Fe₃O₄, and eugenol·Fe₃O₄ on testosterone levels and sperm parameters. MATERIAL AND METHODS: Magnetite nanoparticles were synthesized by the co-precipitation method. After synthesis, eugenol was added to the suspension. Thirty-two adult rats were divided into control (Tween 20 2%; vehicle), eugenol, Fe₃O₄, and eugenol·Fe₃O₄ groups (n = 8/group). Each animal was anesthetized to inject 5 μg of each treatment into caput epididymis (CEUA 35/2023). Seventy days later, the animals were euthanized to collect serum, testis, and epididymis for hormone quantification. Sperm from the cauda epididymis were harvested to assess sperm parameters. RESULTS AND CONCLUSION: FTIR and XRD results confirmed the formation of magnetite and the presence of eugenol in the sample. Epididymal testosterone levels were lower in rats exposed to eugenol (1.4 ± 0.4 ng/mL) and eugenol·Fe₃O₄ (1.7 ± 0.9 ng/mL) than in control rats (3.3 ± 0.3 ng/mL; p < 0.05). Serum (Control: 3.5 ± 2.2; Eugenol: 3.8 ± 2.2; Fe₃O₄: 3.9 ± 1.6; Eugenol·Fe₃O₄: 3.5 ± 0.9 ng/mL) and testicular testosterone (Control: 8.5 ± 1.1; Eugenol: 8.1 ± 1.1; Fe₃O₄: 8.2 ± 1.9; eugenol·Fe₃O₄: 8.8 ± 1.6 ng/mL) did not differ among groups (p > 0.05). Treated rats showed lower sperm motility (Eugenol: 6.0 ± 8.9%; Fe₃O₄: 16.0 ± 30.5%; Eugenol·Fe₃O₄: 12.0 ± 13.0%) than their controls (79.0 ± 5.5%; p < 0.05). The percentage of sperm with normal morphology and membrane integrity reduced in rats exposed to eugenol (p < 0.05), but not in those receiving Fe₃O₄ and eugenol·Fe₃O₄ (p > 0.05). In conclusion, eugenol impaired epididymal testosterone levels and sperm parameters. Nanoparticles of eugenol·Fe₃O₄, in turn, caused less damage to sperm parameters than eugenol.