Triacetyloleandomycin as inducer of cytochrome P-450 LM3c from rabbit liver microsomes.

A cytochrome P-450 LM3 isozyme has been isolated and purified to electrophoretic homogeneity from liver microsomes of New Zealand white rabbits treated with TAO. On the basis of N-terminal sequence analysis and Ouchterlony double diffusion experiments, this isozyme appeared to be closely related to P-450 LM3c isolated from control animals and was designated LM3c (TAO). Anti LM3c (TAO) IgG totally inhibited both erythromycin demethylase and P-450-TAO metabolite complex formation, two monooxygenase activities specifically stimulated by TAO in liver microsomes from male and female rabbits. Moreover, immunoquantitation experiments showed that the level of LM3c (TAO) was increased 10-15 times above control values in liver microsomes from TAO treated male and female rabbits. We conclude that an isozyme identical or closely related to LM3c is the major form of P-450 induced by TAO in rabbit liver microsomes.