INTERACTIONS OF GONADAL-STEROIDS AND PESTICIDES (DDT, DDE) ON GONADUCT GROWTH IN LARVAL TIGER SALAMANDERS, AMBYSTOMA-TIGRINUM

In view of the current worldwide decline in amphibian populations, exp loratory studies are needed to assess the potential for environmental contaminants to act as endocrine disrupters of the amphibian reproduct ive system. The present study investigated the effects of DDT dichloro diphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DD E) on the development of amphibian gonaducts. Larval male and female t iger salamanders (Ambystoma tigrinum), with immature gonads, were imme rsed in a sublethal solution of p,p'-DDE or technical-grade DDT (80% p ,p'-DDT and 20% o,p'-DDT). Additionally, larvae were injected with the steroid hormones estradiol or dihydrotestosterone (DHT). Morphometric s were used to analyze the effects and interactions of steroid and pes ticide treatments on larval gonaducts. Estradiol and DHT stimulated ce ll proliferation and hypertrophy of the mullerian duct epithelium in b oth sexes. Wolffian duct epithelium, however, was stimulated only by D HT treatment. The pesticide DDT antagonized the estrogenic actions of the steroid treatments, and p!pl-DDE acted as an estrogen on the mulle rian ducts of females only. The mullerian ducts of males, and the wolf fian ducts of both sexes, were unaffected by DDT or DDE alone. While c onfirming the previously reported estrogenic actions of estradiol and DHT on urodelean gonaducts, the results contradict the expected estrog enic actions of DDT and antiandrogenic actions of p-p'-DDE. Instead, i n A. tigrinum, technical-grade DDT had an antiestrogenic action and p, p'-DDE an estrogenicaction. (C) 1998 Academic Press.