B.H. JENSEN*; M.H. TAYLOR: The Effects of Estradiol Implants on Lipid Transport in Fundulus heteroclitus
Fundulus heteroclitus (mummichog) is a euryhaline teleost that is common along the western Atlantic coast from the maritime provinces to Florida. This species has a semilunar reproductive cycle that is accompanied by large changes in plasma levels of triglycerides, the production of vitellogenin (vtg), and changes in plasma lipoproteins. Estradiol implants were used in this study to determine the role of estradiol in lipid transport, and gonadal and hepatic growth. Mummichog were collected from the Canary Creek near Lewes, DE in unbaited minnow traps. They were maintained in the laboratory for one month prior to implantation. Silastic implants were inserted in the peritoneal cavity through a small incision. Fish were sacrificed on the third, seventh, and 14th day post-implantation. Gonado- and hepatosomatic indices (GSI and HSI respectively), plasma levels of triglycerides, cholesterol, liproteins, and estradiol were measured. Preliminary results indicate that estradiol reduced GSI, and at low doses also reduced HSI and messenteric fat stores. Estradiol also induced the production of vtg, and at day seven reduced plasma triglyceride levels. Unfortunately, plasma lipoproteins and lipids have yet to be fully analyzed to this point. However, it is clear that estradiol plays an important role in altering lipid transport to accomidate spawning in the mummichog.