Comparison of activities of drug‐metabolizing enzymes in human fetal and adult livers

Abstract

The in vitro capacity of human fetal liver to metabolize 3,4‐benzpyrene, aniline, aminopyrine, and hexobarbital was lower than that of human adult liver from patients with uncomplicated cholelithiasis. Fetal liver drug‐metabolizing capacity, expressed as percentages of adult values, was 2.4, 27.8, 32.0, and 36.1 per cent, respectively, for the four substrates studied. Cytochrome P‐450 content and nicotinamide adenine dinucleotide phosphate (NADPH)—cytochrome c reductase activity in fetal liver microsomes also reflected the lower drug‐metabolizing activity, being 27.4 and 49.2 per cent, respectively, of adult values. Microsomal protein content was about 26 mg per gram wet weight in fetal liver and about 35 mg per gram in adult liver. Recovery of microsomes was 40% to 60% in both fetal and adult livers. All parameters studied exhibited considerable variation, which ranged from three‐ to elevenfold. Fetal drug metabolism, although generally lower than in the adult, may, in some cases, be higher than maternal drug metabolism.