Detecting Benomyl and Its Metabolite Carbendazim Inducing Androgenic Activity in Rats by Using Uterotrophic and Hershberger Assays

Abstract

Both benomyl and carbendazim are widely used systemic fungicides. It has been shown that benomyl and carbendazim induce endocrine-disrupting activity, resulting in reproductive and developmental toxicity, as well as androgen receptor (AR) gene expression in rats. The aim of this study was to link AR induction by benomyl and carbendazim, observed in our previous reports, with the results of Hershberger and uterotrophic assays. In an uterotrophic assay, neither benomyl nor carbendazim, except at 800 mg/kg/day, affected weight of uterus and vagina when compared to the ovariectomized control rats. Co-treatment with 17β-estradiol (E_2) and 200 mg/kg/day benomyl or co-treatment with E_2 and 200, 800 mg/kg/day carbendazim significantly increased uterine weight when compared to treatment with E_2 alone in an uterotrophic assay. This uterotrophic activity might be mediated through AR. Treatment with flutamide alone or in combination with E_2 had no effect on uterine weight. In the Hershberger assay, treatment with 50 and 100 mg/kg/day benomyl increased weight of ventral prostate plus seminal vesicles. Carbendazim or flutamide alone exhibited no effect on reproductive accessory gland weight. Co-treatment with testosterone propionate (TP) and 50 or 100 mg/kg/ day carbendazim, but not benomyl, significantly increased the weight of ventral prostate plus seminal vesicles. Co-treatment with TP and 50 or 100 mg/kg/day flutamide significantly decreased these reproductive accessory gland weights when compared with TP alone. Based on our previous report, carbendazim increases mRNA and protein expression of AR in testis, epididymis and prostate and antagonizes the reduced tissue weights of seminal vesicle and prostate of male offsprings induced by in utero exposure to flutamide in rats. This infers that benomyl and carbendazim increase the weight of ventral prostate plus seminal vesicles through induction of AR expression. Moreover, according to a previous report, TP, an AR agonist, induces fluid retention in uterus by exhibiting androgenic activity, similar to that of benomyl and carbendazim, in an uterotrophic assay. Based on these results, benomyl and carbendazim exhibit an androgenic effect, leading to increased weight of ventral prostate and seminal vesicles and uterine fluid retention in young adult rats. The exact mechanisms require further investigation.