Effect of in utero and postnatal exposure to environmental tobacco smoke on the developmental expression of pulmonary cytochrome P450 monooxygenases

Pulmonary cytochrome P450 monooxygenases metabolize xenobiotic chemicals, including those found in environmental tobacco smoke (ETS). Exposure to ETS beginning at birth has been shown to induce the P450 CYP1A1 by seven days of life. The effects of perinatal exposure to ETS of the rat lung on the expression of CYP1A1, 1B1, 2B1, and NADPH cytochrome P450 reductase were measured using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Timed pregnant dams and their pups were exposed to aged and diluted sidestream cigarette smoke (ADSS) as a surrogate for ETS for four hours/ day from gestational day 5 through postnatal day 21. For all genes analyzed, mRNA could be detected in the fetal lung beginning at gestational day 17 but were not altered by ADSS. In contrast, intraperitoneal injection of dams with beta-naphthoflavone significantly elevated both CYP1A1 and 1B1 at gestational day 21, indicating that these genes are inducible. Continued exposure to ADSS significantly induced CYP1A1 but not other P450 genes as early as one day after birth.. We conclude that (1) ADSS induces pulmonary CYP1A1 in the first day of life; (2) fetal cytochrome P450 genes are not induced by maternal exposure to ADSS; and (3) in the fetal lung, CYP1A1 and 1B1 can be induced by beta-naphthoflavone.