(PM259) Effects of carrier solvent usage and selection on the vitellogenin (Vtg) mRNA response in the male fathead minnow (Pimephales promelas).
Lehr, R1, Patel, V2, Denslow, N2, Ankley, G3, Swackhamer, D1, 1 University of Minnesota, Minneapolis, MN, USA2 University of Florida, Gainesville, FL, USA3 United States Environmental Protection Agency - Mid-continent Ecological Division, Duluth, MN, USA
ABSTRACT- Vitellogenin induction in male fathead minnows (Pimephales promelas) has been widely used as a bioindicator of environmental estrogen exposure. Despite the widespread use of this assay, there exists a large variability amongst the protocols used to conduct fathead minnow exposures. One of the common differences among exposure protocols is the selection and use of an organic carrier solvent to enhance toxicant delivery. To test the effect of differential carrier solvent usage on the Vtg mRNA endpoint, we exposed male fathead minnows to a series of doses (5, 10, 50 and 100 ng/L) of 17a-ethynilestradiol (EE2) using four different toxicant delivery carriers (water, ethanol, triethylene glycol and dimethyl sulfoxide). All fish were exposed for 48-hrs following the USEPA standard methods for static exposure. Results from this experiment indicate that use of an organic carrier solvent to enhance toxicant delivery significantly increases Vtg mRNA induction, relative to entirely aqueous based exposures. Among the different carrier solvents, dimethyl sulfoxide elicited the most pronounced estrogenic response. These results suggest that carrier solvent use/choice is a critical component of fathead minnow exposures and that some of the large variability in sensitivity and relative response of both Vtg protein and mRNA results reported in the literature may be as a result of differential carrier solvent usage.
Key words: Ethinylestradiol, Fathead Minnow, mRNA, Carrier Solvent