ALTERATIONS IN STEROIDOGENESIS IN ALLIGATORS (ALLIGATOR-MISSISSIPPIENSIS) EXPOSED NATURALLY AND EXPERIMENTALLY TO ENVIRONMENTAL CONTAMINANTS

Many environment contaminants alter the reproduction of animals by alt ering the development and function of the endocrine system. The abilit y of environmental contaminants to alter the endocrine system of allig ators was studied both in a descriptive study in which juvenile alliga tors from a historically contaminated lake were compared to animals fr om a control lake and in an experimental study in which hatchling cont rol alligators were exposed in ovo to several endocrine-disrupting: st andards and two modern-use herbicides. Endocrine status was assessed b y examining plasma hormone concentrations, gonadal-adrenal mesonephros (GAM) aromatase activity, and gonadal histopathology. In the descript ive study juvenile alligators from the contaminated lake had significa ntly lower plasma testosterone concentrations (29.2 pg/ml compared to 51.3 pg/ml), whereas plasma 17 beta-estradiol concentrations did not v ary when compared to controls. GAM aromatase activity was significantl y decreased in the alligators from the contaminated lake (7.6 pmol/g/h r compared to 11.4 p/mol/g/hr). In the experimental study, the endocri ne-disrupting standards had the expected effects. 17 beta-Estradiol an d tamoxifen caused sex reversal from male to female, with a correspond ing increase in aromatase activity. Vinclozolin had no apparent effect on male or female alligators. Among the herbicides tested, atrazine i nduced GAM aromatase activity in male harchling alligators that was ne ither characteristic of males nor females, although testicular differe ntiation was not altered. Exposure to 2,4-dichlorophenoxyacetic acid h ad no effect on the endocrine parameters that were measured. Together, these studies show that exposure to sonic environmental chemicals (su ch as atrazine) can alter steroidogenesis in alligators, but the endoc rine alterations previously noted for Lake Apopka, Florida, alligators can not be fully explained by this mechanism.