Meeting Abstract
A number of chemicals released into the environment mimic the action of the steroid hormone estrogen. These environmental estrogens pose potential health risks to humans and wildlife by disrupting physiological and developmental processes. Many laboratories have been using in vivo bioassays for environmental estrogens that are based on induction of the egg yolk precursor protein vitellogenin (vtg). The vast majority of vtg bioassays have been developed for fish species. In contrast, there have been few studies using vtg as a biomarker in tetrapods. My laboratory, in collaboration with others, has been developing tests for estrogenicity in tetrapods that involve evaluation of induction of the vtg protein in serum by specific immunoassays and the induction of hepatic vtg mRNA by RT-PCR. These vtg bioassays have been used for assessing endocrine disruption in a variety of tetrapods, including amphibians (tiger salamander, leopard frog, and African clawed frog) and reptiles (painted turtle, red-eared slider turtle, Loggerhead sea turtle, Olive Ridley sea turtle, and Morelet’s crocodile). These studies have demonstrated both the utility and the limitations of vtg induction’s use as a biomarker for endocrine disruption. Vtg bioassays in tetrapods are quite useful for studies of reproductive cycles and patterns, and they may also be used to reveal exposure to higher levels of endocrine disruptors. However, vtg induction in tetrapods may not be as sensitive to low levels of environmental estrogens as it is in fishes, especially where serum vtg is concerned. There is a need for new, preferably minimally invasive, tests of vtg mRNA induction to increase the sensitivity of tetrapod endocrine disruption assays.
