Neonatal treatment with phenobarbital, zixoryn and chloramphenicol lack of imprinting effect of zixoryn on microsomal enzyme activities.

Two potent microsomal enzyme inducing agents, phenobarbital and flumecinol (Zixoryn) as well as the microsomal enzyme inhibitor chloramphenicol (Chlorocid) were given subcutaneously to newborn rats in the first 5 days of their life. Microsomal cytochrome P-450 and b5 content and various cytochrome P-450 and P-448 dependent enzyme activities were measured at the age of 20 weeks. Phenobarbital had positive imprint effect on aminopyrine N-demethylase activity in female and on aniline hydroxylase activity in male rats. Flumecinol had no imprint effect. Chloramphenicol had a positive imprint on aniline hydroxylase activity in male rats. Sex differences in microsomal enzyme activities were not affected by the xenobiotics used.