Estrogen Stimulation of Vitellogenin Production in the Kemp's Ridley Sea Turtle
Heck, Jennifer A.
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Studies of reproductive endocrinology are necessary for the conservation of critically endangered species such as the Kemp's Ridley sea turtle, Lepidochelys kempi. Among reproductive hormones, the role of estrogen is poorly understood. This examination of the effects of estrogen on hepatic production of vitellogenin, the precursor to yolk protein in oocytes of all lower vertebrates, was conducted to enhance understanding of estrogen cycles as they correlate with the dynamics of ovarian growth in these animals. L. kempi were injected with estradiol and blood was sampled over a 12 week period. During this time, it was found that serum total protein, phosphoprotein and total calcium levels increased significantly. Associated with these changes, a novel band of 205,000 daltons was observed on polyacrylamide gels. Unlike findings in teleost fishes, estrogen did not influence free thyroid hormone binding to plasma proteins in L. kempi. It was concluded that estrogen does induce vitellogenesis in these animals and that the vitellogenin obtained is very similar to that found in other species of fish, amphibians and turtles. This protein may be used in the future to develop techniques which will refine the study of ovarian development in these animals, thereby creating opportunities for conservation of their populations.