Some Observations on the Microsomal Electron Transport System and Activities of Drug Oxidizing Enzymes in Human Liver

1. Aniline-induced difference spectrum in post-mortem human liver microsomes was recognized as type II similar to that in rat liver. Hexobarbital- and aminopyrineinduced P-450 difference spectra were also of type II in human, but they were different from those in rat liver microsomes.2. There was no correlation between enzyme activities of the NADPH-linked electron transport system in liver microsomes and aniline hydroxylase activity in human liver, which was similar to that of rat liver. The activity of hydroxylation. of hexobarbital, a type I compound, in human was lower than that in rat liver, and a similar result was observed when aminopyrine was used as substrate.