The Effects of Vitamin B Complexes on AAF Hydroxylation by Rat Liver Microsomal Cytochrome P-450

The effects of vitamin B complexes on both ring and N-hydroxylation of 2-ace-tylaminofluorene by rat hepatic microsomal fraction were studied.

In the presence of thiamine-Hcl during incubation, the total hydroxy-AAF was increased by 50.3%. 0.1mM and 1.0mM riboflavin inhibited only total hydroxy-AAF with 56.7% and 85.0 whereas N-hydroxy AAF was increased to some extent. 1.0mM niacin did not have much effect on the total hydroxy-AAF, but 0.1mM niacin decreased the total dydroxy-AAF by 28.6%. Presence of p-amino-benzoic acid, calcium pantothenate, pyridoxal-Hcl or vitamin B₁₂ inhibited the total hydroxy-AAF to some extent. But the radio of ring-and N-AAF hydroxylation was not changed by these vitaminn B complexes.

Our present results suggest that vitamin B complexes were not effective in vitro metabolism of 2-AAF to N-hydroxy AAF(activation step of AAF) by a cytochrome p-450 dependent mixed function oxidase system.