By the treatment of newborn male rats with monosodium glutamate (MSG), microsomal benzo[a]pyrene hydroxylation, propoxycoumarin O-depropylation, and testosterone (T) 6β- and 2βhydroxylations in the adult rats were decreased significantly, while microsomal aniline and T 7αhydroxylations were increased. However, the treatment of newborn female rats did not significantly alter any of the drug-metabolizing activities examined, except that T 6β-hydroxylation and androstenedione formation were slightly increased. The hepatic contents of male-specific cyt. P-450, P-450-male and P-4506β, which show high catalytic activities on respective T 16α/2α-, and T 6β/2β-hydroxylations, decreased in MSG-treated male rats. The level of the female specific enzyme, P-450-female, slightly decreased in the MSG-treated female rats, whereas higher phénobarbital (PB)-induction of PB-inducible isozymes, P-450b and P-450e, was observed in MSG-treated than in control female rats. These results are consistent with the idea that disruption of a pulsatile secretion of growth hormone, which is induced by the neonatal MSG treatment, leads to changes in drug metabolizing activities through the alteration of the levels of sex-specific cyt. P-450s, but also indicate that MSG-treated rats are not an animal model equivalent to hypophysectomized rats.
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