Characterization of human fetal hepatic cytochrome P-450-associated 7-ethoxyresorufin O-deethylase and aryl hydrocarbon hydroxylase activities by monoclonal antibodies.
Two cytochrome P-450-dependent enzyme activities, 7-ethoxyresorufin O-deethylase (ERDE) and aryl hydrocarbon hydroxylase (AHH) were measured in liver microsomes from 7 human fetuses. Monoclonal antibodies (MAb) to a 3-methylcholanthrene-induced (MAb 1-7-1) and a phenobarbital-induced (MAb 2-66-3) rat hepatic cytochrome P-450 were used to measure the contribution of the MAb-defined, epitope-specific cytochromes P-450 to the total reaction measured for the above activities. MAb 1-7-1 inhibited fetal hepatic ERDE activity to a variable extent (from 0 to 100%, 34 in average), but had only negligible effects on AHH activity (mean inhibition 9%). The contribution of induction by cigarette smoking to the variability of ERDE inhibition by MAb 1-7-1 remained unclear. MAb 2-66-3 inhibited ERDE activity by 18% and AHH activity by 12%. In comparisons with earlier studies on adult liver and placental microsomes, the present results with fetal liver suggest that there are differences in cytochrome P-450-associated ERDE and AHH activities between these tissues, which might be due to different tissue-specific isoenzyme patterns.
D000911:Antibodies, Monoclonal; D001189:Aryl Hydrocarbon Hydroxylases / Q000032:analysis*; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis*; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000196:embryology / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology; D010088:Oxidoreductases / Q000032:analysis*; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy
D000911:Antibodies, Monoclonal; D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1