The fungicide procymidone alters sexual differentiation in the male rat by acting as an androgen-receptor antagonist in vivo and in vitro

Abstract

Procymidone is a dicarboximide fungicide structurally related to the well-characterized fungicide vinclozolin. Vinclozolin metabolites bind to mammalian androgen receptors (AR) and act as AR antagonists, inhibiting androgen-dependent gene expression in vivo and in vitro by inhibiting AR-binding to DNA. The current study was designed to determine if procymidone acted as an AR antagonist in vitro and to describe the dosage levels of procymidone that alter sexual differentiation in vivo. In vitro, procymidone inhibited androgen from binding the human AR (hAR) in COS (monkey kidney) cells transfected with hAR at 3.16 μM. In vitro, procymidone acted as an androgen antagonist, inhibiting dihydrotestosterone (DHT)-induced transcriptional activation at 0.2 μM in CV-1 cells (cotransfected with the hAR and a MMTV-luciferase reporter gene). In vivo, maternal procymidone exposure at 0, 25, 50, 100, or 200 mg kg⁻¹ day⁻¹ during gestation and early lactation (gestational day 14 to postnatal day 3) altered reproductive development of male offspring at all dosage levels tested. Male offspring exhibited shortened anogenital distance (at 25 mg kg⁻¹ day⁻¹ and above), permanent nipples, reduced weight of several androgen-dependent tissues (levator ani and bulbocavernosus muscles, prostate, seminal vesicles, Cowper's gland and glans penis), and malformations (hypospadias, cleft phallus, exposed os penis, vaginal pouch, hydronephrosis, occasional hydroureter, epididymal granulomas, and ectopic, undescended testes). In addition, perinatal procymidone treatment had a marked effect on the histology of the lateral and ventral prostatic and seminal vesicular tissues of the offspring (at 50 mg kg⁻¹ day⁻¹ and above). These effects consisted of fibrosis, cellular infiltration, and epithelial hyperplasia. This constellation of effects is similar to that produced by perinatal exposure to vinclozolin. However, procymidone appears to be slightly less potent in inducing malformations than vinclozolin by a factor of about two. In summary, the antiandrogenic activity of procymidone was demonstrated in vivo and in vitro in cell lines transfected with hAR. Since the role of androgens in mammalian sexual differentiation is highly conserved, it is likely that humans would be adversely affected by procymidone in a predictable manner if the human fetus was exposed to sufficient levels during critical stages of intrauterine and neonatal life.