Prenatal alcohol exposure alters the maternal hypothalamic-pituitary-adrenal-axis, elevating concentrations of glucocorticoids. Glucocorticoids exert their effects via binding to the glucocorticoid receptor (GR), for which there are a number of isoforms that regulate specific downstream signaling pathways. This study aimed to characterise the GR isoform profile in the placenta and fetal liver in the rat following periconceptional alcohol exposure (PCE).
Sprague-Dawley dams were given 12.5% ethanol (PCE) or 0% ethanol (control) liquid diet from 4 days prior to 4 days after conception (6-9 litters/group). At embryonic day 10 (E10), dams were given standard chow. Late gestation (E20) fetuses and placentas were collected and measured/weighed. All fetuses/placentas were sexed. Placentas were separated into labyrinth and junctional zones for molecular analysis and fetal livers collected (only one of each sex/litter used for each analysis). Tissues were snap-frozen for analysis of GR isoforms by western blot and densitometry. Cytoplasmic and nuclear protein fractions were isolated at extraction and were analysed separately.
Multiple GR isoforms were identified within the fetal liver (12 isoforms, including GRα, GR-P, GRα-D1-D3) while a different profile of isoforms was identified in the placenta (13 isoforms, including GRα-A, and GRα-C). We also identified previously uncharacterised GR-positive bands in both tissues. Isoform profiles varied by cellular compartment and, in the placenta, by zone. PCE induced changes in the GR isoform profile in each tissue in a sex-specific manner, with females showing alterations in the placental labyrinth and males showing alterations in cytoplasmic liver fractions. Specific isoforms were also significantly correlated with fetal, liver and placental growth.
These results have identified, for the first time, GR isoforms in the rat placenta and fetal liver, and suggest that PCE alters the GR isoform profiles in these tissues. This data provides a possible mechanism for glucocorticoid-mediated programming of offspring metabolic disease following prenatal alcohol exposure.