Comparison of the Activities of Drug‐metabolizing Enzymes in End‐term Foetal and Maternal Livers of the Rabbit

Abstract

Abstract: The components of drug biotransformation complex in the microsomal membranes of end‐term foetal and maternal livers were compared. The end‐term foetal liver was found to possess NADPH cytochrome c reductase and cytochrome P‐450 at levels of 38 and 18% of the maternal level, respectively. The foetal liver also had p‐nitroanisole O‐demethylase activity of 29% of that in maternal hepatic microsomes. However, the aryl hydrocarbon hydroxylase activity was very low in foetal liver (only about 5% of that in maternal liver). UDPGlucuronosyltransferase (p‐nitrophenol as aglycone) activity in the foetal liver was at the level of 36% of that in maternal liver, when measured in “native” microsomes. The measurable glucuronosyltransferase activity in foetal liver could be increased 10‐fold by digitonin, 5‐fold by trypsin and 2‐fold by phospholipase A treatments, as compared to 6‐fold by digitonin and 3‐fold by both trypsin and phospholipase A in maternal liver microsomes.