Hepatic mixed-function oxidase system and microsomal lipid peroxidation in rats treated with a synthetic immunomodulator, N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP).

Effects of synthetic muramyl dipeptide (MDP) on activity of liver microsomal mixed-function oxidase system and on the susceptibility of liver microsomes to lipid peroxidation, were tested in rats at intervals of 1 or 24 hours after single i.p. injection of MDP (1 mg per animal). No significant changes were found in levels of cytochrome P-450 and b5, microsomal heme, or in activities of aniline hydroxylase, ethylmorphine demethylase, glucuronide transferase or cytosol glutathione-S-transferase. However, significantly less (about 45%) TBA-reactive material accumulated in microsomal samples at the 1 h-interval after the MDP administration. The same inhibitory effect of MDP on lipid peroxidation was shown in vitro (in 1 mM concentration) after incubation of microsomes with the NADPH/ADP/Fe system.