The behaviour of microsomal mono-electron carriers in human placenta during late pregnancy

The activities and the content of enzymes involved in mixed function oxidase systems (cytochromes P-450 and b5, NADPH-cytochrome c reductase and NADH cytochrome b5 reductase) in microsomes from 114 human placentae were found to increase from the 34th up to the 38th-39th week of gestation and later to decrease until the 43rd week. Such a process can be related to the following: (i) the phospholipid content of microsomal membranes; (ii) the protein synthesis possibly induced by steroids such as androstenedione and testosterone.