Induction of Calbindin-D9k messenger RNA and protein by maternal exposure to alkylphenols during late pregnancy in maternal and neonatal uteri of rats

Environmental chemicals are proposed to possess hormonelike properties, such as mimicking natural hormones, inhibiting the action of hormones, and inducing abnormal gene expression. Among environmental chemicals, the alkylphenol products (APs), octylphenol (OP) and nonylphenol (NP), are derived from alkylphenol ethoxylates and have been reported to be environmentally persistent. Thus, in the present study, we examined the effect of two APs, OP and NP, on the expression of Calbindin-D-9k (CaBP-9k) following maternal exposure during late pregnancy in maternal and fetal uteri. Treatment with a high dose (600 mg/kg body weight [BW]) of OP and NP resulted in an induction of CaBP-9k mRNA at Day 5 of lactation, as did a single treatment with diethylstilbestrol (DES) and 17beta-estradiol (E2) in maternal uteri. The expression of CaBP-9k mRNA was also induced following treatment with a high dose (600 mg/kg BW) of OP, transferred from the mother, exposed to fetuses during late pregnancy, and persisted through Day 5 of lactation. It is of interest that treatments with high doses of OP (400 and 600 mg/kg BW) reduced the expression of maternal estrogen receptor alpha (ERalpha) mRNA, as E2 did. However, all doses of NP resulted in an inhibition of neonatal ERalpha, while only the high does of OP (600 mg/kg BW) induced the reduction of neonatal ERalpha mRNA expression, as E2 did. Parallel to mRNA, the expression of CaBP9k protein was significantly induced by treatment with a high dose of OP and NP. In conclusion, maternal exposure to APs, OP and NP, during late pregnancy increased the expressions of CaBP-9k mRNA and protein in maternal and neonatal uteri. These results suggest that the absorption and distribution of environmental estrogenic compounds in maternal and neonatal uteri are extremely rapid, and these chemicals can easily pass though the placenta during pregnancy to affect functions of neonatal reproductive tissues.