The N-oxidation of pyridine, 3-methylpyridine and 3-chloropyridine was inhibited by SKF525A and DPEA. The C-oxidation of 3-methylpyridine was also inhibited by these compounds. 2. The N-oxidation of these pyridines was also inhibited by various other nitrogenous substrates including n-octylamine. 3. Incubation in an atmosphere of carbon monoxide resulted in inhibition of both C- and N-oxidation of 3-methylpyridine. 4. Any treatment of microsomes which resulted in a reduction of cytochrome P-450 also produced a concomitant fall in N-oxidation of the pyridines. 5. Pretreatment of animals with phenobarbitone resulted in an increase in the N-oxidation of the pyridines. Pretreatment with 3-methylcholanthrene had no appreciable effect on the N-oxidation of the pyridines in vitro.
