Placental transfer of the soy isoflavone genistein following dietary and gavage administration to Sprague Dawley rats

Genistein, the principal soy isoflavone, has estrogenic activity and is wid ely consumed for putative beneficial health effects. The goal of the presen t study was to measure placental transfer of genistein in rats as a possibl e route of developmental exposure. Pregnant Sprague-Dawley rats were admini stered genistein orally, either by diet or by gavage. Concentrations of gen istein aglycone and conjugates were measured in maternal and offspring seru m and brain using HPLC with isotope dilution electrospray tandem mass spect rometry. Although fetal or neonatal serum concentrations of total genistein were approximately 20-fold lower than maternal serum concentrations, the b iologically active genistein aglycone concentration was only 5-fold lower. Fetal brain contained predominately genistein aglycone at levels similar to those in the maternal brain. These studies show that genistein aglycone cr osses the rat placenta and can reach fetal brain from maternal serum genist ein levels that are relevant to those observed in humans. (C) 2001 Elsevier Science Inc. All rights reserved.