Biochemical Effects of Radioprotective Agents on the Liver Microsomal Hydroxylating System: in Vitro Studies

Summary

The action of two radioprotectors—cysteamine and cystamine—on the liver microsomal multi-enzyme hydroxylating system, a key system in drug and biological compounds metabolism, has been studied. Their effects have been systematically analysed at the level of individual enzyme activities and global functions. The two compounds are quite inactive on NADPH and NADH cytochrome c reductase activities, but slightly denature the cytochrome P₄₅₀ into cytochrome P₄₂₀. Furthermore, they do inhibit to some extent (30 per cent at 10⁻² M) the rate of codeine hydroxylation and totally suppress (at 10⁻² M) the NADPH-induced lipid peroxidation which occurs during enzymatic functioning. These results are discussed in the light of the toxicity of radioprotectors.