Meeting Abstract
Maternal effects, the nongenetic changes in offspring due to the maternal environment, can have a large influence on offspring phenotype. Glucocorticoids (GCs), steroids involved in the stress response, can be passed from mother to offspring and influence development. Recent evidence suggests that embryos can regulate their exposure to maternal GCs. Given this active regulation of the early endocrine environment, we examined how site of injection (yolk vs. albumen) and dose affected embryonic exposure to corticosterone (CORT). We injected eggs of Japanese quail (Coturnix japonica) with a low or medium dose (within physiological range) or a high dose (pharmacological) of [3H]-CORT, and then collected eggs after 6 or 9d of development. Eggs were then separated into albumen, yolk, and embryonic tissue to identify the presence of free and conjugated steroids while CORT and its metabolites were identified through thin layer chromatography (TLC). We found that both site of injection and dose influenced embryonic exposure to CORT. Yolk-injected eggs had more free and conjugated steroids in the yolks compared to albumen-injected eggs at both days of development. The level of free steroids in the yolk was lower at lower doses and decreased during development, while the conjugated steroids in the yolk increased with dosage and during development. In addition, the level of free and conjugated steroids in the embryonic tissue were highest early in development and at higher doses. TLC analysis detected a number of CORT metabolites along with CORT in the embryo which suggests that while a buffer plays an extensive role in metabolizing steroids, this buffer can be overwhelmed at higher maternal steroid levels.
