Relationship between induction of ethoxyresorufin-O-deethylase (FROD) and insulin binding in tissues of rat placenta

The authors have reported that treatment of pregnant rats with β-naphthoflavone (β NF) resulted in differential induction of EROD in placental tissues. This study further characterized the induction of EROD in placental tissues by 3-methylcholanthrene (3MC), and investigated whether there is a relationship between the induction of EROD and insulin binding to the placental tissues. β NF (15 mg/kg) or 3-MC (30 mg/kg) was administered i.p. on gestation day 14. On day 15, placentae were dissected into basal zone (BZ) and labyrinth (LA) tissues. EROD activity was measured by fluorimetric assay in homogenates of BZ or LA. Plasma membranes of BZ and LA were prepared and assayed for insulin binding using [125I]-insulin. In summary, treatment with β NF as well as 3-MC differentially induced EROD in LA compared to BZ tissue, while neither treatment affected the binding of insulin to BZ and LA membranes