Xenoendocrine disrupters: laboratory studies on male reproductive effects

Wildlife from ecosystems contaminated with endocrine disrupting chemicals (EDCs) display a variety of reproductive alterations including cryptorchidism in the Florida panther, small baculum in young male otters, small penises in alligators, sex reversal in fish, and altered social behavior in birds. It has been proposed that EDCs also may have contributed to increases in testicular cancer and hypospadias and the reported decline in human sperm counts. Combined in vivo and in vitro studies are necessary to fully characterize EDC induced alterations of reproduction. We have identified several pesticides (vinclozolin, procymidone, p,p'-DDE) which bind rat and human androgen receptors, block androgen-induced gene expression in vitro and in vivo, delay puberty, reduce sex accessory gland size and alter sex differentiation in the male rat. Some of the phthalates, which are estrogenic in vitro but not in vivo, cause malformations in male rats that appear to result from antagonism of androgens in utero. In contrast, xenoestrogens affect male offspring but they are not malformed or infertile. Prenatal administration of an Ah receptor agonist (2,3,7,8-TCDD or PCB 169) produces a different spectrum of effects including reduced ejaculated sperm numbers in male rats.