Effects of Bisphenol A exposure on growth and onset of metamorphosis in Drosophila melanogaster. Amber K Weiner, Ashley Parker, AnnJosette Ramirez, Kara Bennett, Kristin Johndreau, Caroline Rachfalski, Sheryl Smith. Biology, Arcadia University, Glenside, PA.

   Bisphenol A (BPA) is a high production volume chemical used in the manufacture of polycarbonate plastics, epoxy resins, food packaging, thermal paper, dental composites and sealants and other products. Human exposure to BPA through dietary and non-dietary sources has been well-documented. In numerous vertebrate studies, BPA has been reported to act as a teratogen as well as an endocrine disruptor. Conversely, BPA studies in a variety of invertebrate models suggest that BPA exerts its effects primarily through endocrine disruption, where alterations in fecundity, sex ratio, onset of sexual maturity and other effects have been reported. The mechanisms underlying these effects are incompletely understood and a substantial number of studies report a variable concentration-dependent toxicity. We investigated the effects of BPA exposure in Drosophila melanogaster and observed a significant increase in larval size with an administered exposure of 0.1 mg/L. We further found that exposure to BPA at concentrations of 10 mg/L and 0.1 mg/L resulted in an earlier onset of metamorphosis than non-treated control larvae. Treatment with 1 mg/L BPA had no effect on the onset of pupariation. Body size in Drosophila is determined by growth rate and length of time to reach metamorphosis. These processes are governed, in part, through the effects of the insulin-signaling pathway and the ecdysone signaling pathway. We examined the expression of Ecdysone receptor (EcR) and broad (Br), two ecdysone-responsive genes critical for the processes of molting and metamorphosis, and found that these genes are expressed earlier in development, at 48 hours, in BPA-treated larvae versus non-treated larvae, where the expression of EcR and Br was observed at 72 hours of development. These findings suggest that BPA exerts its effects through endocrine disruption in Drosophila. A gene expression analysis is currently underway to elucidate possible mechanisms underlying variable dosage effects.