RESUMO
Chemosterilants have long been used in sterilization programs for managing pet, stray, and wild animals but adverse effects such as trauma, incomplete responses to treatment, and complete abolition of gonadal sources of testosterone often occurs. This study describes the biosterilant effects of administering three doses of Bacillus thuringiensis kurstaki HD-73 (Bt 5, 50, and 250 mg/kg; 20 rats/dose) extract in adult male Wistar albino rats on testicular parameters, function, histology, and a number of biochemical markers of overall health, free radical production, and cell proliferation. Intratesticular administration of Bt extract to rats induces testicular oxidative stress and damages and consequently, perturb spermatogenesis, degeneration of testis, reduction in testes size, and depletion of testosterone and antioxidant enzyme concentrations in a dose-dependent manner because of free radical-mediated lipid peroxidation. No morbidity or mortality adverse effects were observed in both the saline control and Bt extract-treated rats. Significant variation was noted in clinical manifestations, weight and volume of testes, and hormonal and biochemical profiles between Bt doses in comparison with the saline control. Aspermia/azoospermia (100%) resulted in Bt-treated rats without any adverse effects. Histopathological analysis showed degeneration, necrosis, vacuolation, fewer germ cells, formation of multinucleated giant cells, and a lack of elongated spermatids in atrophic seminiferous tubules in Bt extract-treated groups in the presence of low concentrations of testosterone, antioxidant enzymes, and suppression of germ cell proliferation. Dose-dependent effects were evident in most parameters that were measured. The vast array of tests that were undertaken also provides some important indicators of the physiological effects associated with the treatments that were applied. Intratesticular injection of Bt extract impairs spermatogenesis and induces permanent sterility in rats.
