Molecular toxicology on cytochrome P-450 in human fetal livers.

Among mammalian species, humans and monkeys are sole species which possess cytochrome P-450 in the liver in fetal life. Cytochrome P-450 catalyzes oxidations of a wide variety of compounds including steroids, drugs and toxicants. Thus, the purpose of this study was to examine the toxicological significance of human fetal cytochrome P-450. Firstly, we found that human fetal livers were capable of activating numbers of carcinogenic compounds. Secondly, the capacity of human fetal cytochrome P-450 to activate mutagens and carcinogens was confirmed using purified forms of cytochrome P-450. For this, we purified four forms of cytochrome P-450 from human fetal livers. Lastly, we could isolate a cDNA clone coding for P-450HFLa which is one of the major forms of cytochrome P-450 in human fetal livers. Utilizing synthesized cD-NAs as probes, we found that this form of cytochrome was expressed specifically in fetuses.