title: Studies of cytochrome synthesis in rat liver.
abstract: The incorporation of radioactive amino acids and of delta-amino[2,3-(3)H(2)]laevulinate into rat liver cytochromes b(5) and c and cytochrome oxidase has been examined with and without protein-synthesis inhibitors. Cycloheximide promptly inhibits labelling of both haem and protein for cytochrome c in parallel fashion. Although incorporation of (14)C-labelled amino acid into microsomal cytochrome b(5) is also rapidly inhibited, cycloheximide incompletely inhibits haem labelling of cytochrome b(5) and cytochrome a+a(3), and inhibition occurs only after repeated antibiotic injections. The possibility of apo-protein pools, or of haem exchange, with a rapidly renewed ;free' haem pool, is considered. Consistent with this model is the observation of non-enzymic haem exchange in vitro between cytochrome b(5) and methaemoglobin. Chloramphenicol, injected intravenously over 5h, results in a 20-40% decrease in incorporation of delta-amino[2,3-(3)H(2)]laevulinate into haem a+a(3) and haem of cytochromes b(5) and c. With the dosage schedule of chloramphenicol studied, amino acid labelling of total liver protein and of cytochrome c was not inhibited. Similarly, ferrochelatase activity was not decreased.
authors.affiliation: Departments of Medicine and Biochemistry, The University of Chicago Pritzker School of Medicine, and Argonne Cancer Research Hospital, Chicago, Ill. 60637, U.S.A.
authors.forename: R
authors.initials: R
authors.lastname: Druyan
authors.forename: S
authors.initials: S
authors.lastname: Jakovcic
authors.forename: M
authors.initials: M
authors.lastname: Rabinowitz