ESTROGEN INDUCTION OF PLASMA VITELLOGENIN IN THE KEMPS RIDLEY SEA-TURTLE (LEPIDOCHELYS-KEMPI)

Estrogen stimulation of the production of the yolk protein precursor v itellogenin was demonstrated in immature Kemp's ridley sea turtles. 17 beta-Estradiol injection elicited an increase in serum estrogen, prot ein, protein phosphorus, and total calcium within 7 days. Associated w ith these changes was the appearance of a single, dimethylformamide-pr ecipitatable, 205-kDa estradiol-induced serum protein, which became th e predominant serum protein identified by polyacrylamide gel electroph oresis. The effects of estradiol injection were maintained for 3 month s following termination of estradiol administration, despite a decline in serum estrogen levels. Although studies in other species have indi cated that changes in circulating vitellogenin levels can influence th yroid hormone transport, no changes were observed throughout the study in total blood levels of thyroxine or triiodothyronine or protein bin ding of these hormones. We conclude that in the immature Kemp's ridley estrogen induces the synthesis and secretion of a vitellogenin which resembles that of other reptiles, but which does not influence thyroid hormone transport. The prolonged presence of vitellogenin in the bloo d may be due to a lack of an active ovarian uptake mechanism in these immature animals. (C) 1997 Academic Press.