[Influence of 3,5,3'-triiodo-L-thyronine on the hepatic enzyme activities responsible for the metabolism of xenobiotics during the development of the chick embryo].

The influence of thyroid hormones on microsomal drug metabolizing enzymes was studied in hypothyroid newborn rats and chick embryos. Administration of 3,5,3'-triiodo-L-thyronine strongly decreased the microsomal cytochrome P 450 content in hypothyroid new-born rats and thus could render the rat pup more susceptible to hepatotoxicity from drugs. The drug metabolizing system in 20 days old chick embryos was less sensitive to the effects of thyroid hormone, but administration of phenobarbital was accompanied by a strongly induction effect on microsomal enzyme activities.