Meeting Abstract
44.5 Jan. 6 Multiple vitellogenins and their physiological regulation by 17&beta-estradiol and two endocrine disruptors in the Mozambique tilapia, Oreochromis mossambicus DAVIS, L.K.*; HIRAMATSU, N.; SULLIVAN, C.; HIRANO, T.; GRAU, E.G.; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe; Hokkaido National Fisheries Research Institute, Kushiro, Japan; North Carolina State University, Raleigh; Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe lkdavis@hawaii.edu
Sequence analysis revealed three distinct vitellogenin (Vg) types, categorized as VgA, VgB, and VgC, in the Mozambique tilapia (Oreochromis mossambicus), making this species one of only a few teleost species with three forms of Vg. The objectives of these studies were to characterize the physiology of multiple forms of Vg, by examining the effects of an intraperitoneal injection of 17-&beta-estradiol (E2), and the estrogenic pesticides o,p�-DDE and heptachlor on their hepatic expression in male fish. A single injection of E2 at 5 &mug/g body weight into male tilapia significantly increased plasma levels of Vg within 1 day and continued to increase over the 5 day experiment. Hepatic expression of all three Vg genes increased markedly 1 day after E2 injection, and high levels of expression were maintained until day 5. The expression pattern of estrogen receptor &alpha (ER&alpha) showed an identical pattern to Vgs A-C, suggesting a mediating role in Vg regulation. In a second experiment lasting 10 days, fish were given a single injection of 100 &mug/g o,p�-DDE, heptachlor, or 5 &mug/g E2. Similar to the first experiment, plasma Vg and expression of Vgs A-C and ER&alpha were significantly increased by E2. While neither pesticide had an effect on plasma Vg, expression of Vgs A-C were significantly increased by o,p�-DDE, but not heptachlor after 10 days. ER&alpha mRNA levels were not altered by either pesticide. These data suggest that within 1 day, E2 increases plasma Vg by stimulating expression of Vgs A-C and ER&alpha while o,p’-DDE and heptachlor do not act via the same mechanism at the dose used in this study.
