Meeting Abstract
P1.75 Tuesday, Jan. 4 Specific estrogenic activity and intra-specific variation in avian egg size: application of an ER-CALUX bioassay FRONSTIN, M.M.*; WILLIAMS, T.D.; Simon Fraser University; Simon Fraser University mfronsti@sfu.ca
Avian egg mass varies considerably within species but the mechanisms underlying this phenotypic plasticity are largely unknown. For example, environmental factors (e.g. food supplementation, ambient temperature) and aspects of female phenotype (e.g. female mass, age, experience) appear to have only minimal effects on egg size. Previous attempts to relate circulating hormone levels (e.g. estradiol) to functional, hormonally-mediated outputs (yolk precursor levels, follicle or egg size) have also met with little success. We hypothesized that one reason for this might be that most circulating estradiol is bound by sex-hormone binding globulin and is unable to activate its nuclear hormone receptors. Most commonly used hormone assays measure both bound and unbound, i.e. ‘total’ hormone levels. In this study we aimed to measure unbound or “biologically active” estradiol activity in plasma from egg producing female zebra finches (Taeniopygia guttata) through the use of a recombinant cell bioassay. The chemically activated luciferase expression (CALUX) bioassay will employ BG1Luc4E2 cells that produce firefly luciferase (an easily measurable protein) in response to estrogenic compounds. We then relate biologically or physiologically active estradiol levels to aspects of female reproductive phenotype (egg size, clutch size).
