Enhanced hepatic chromatin protein methylation induced by triiodothyronine treatment of the rat.

A pharmacological dose of 3,3',5-triiodo-L-thryonine (200 microgram/100g) that induce marked DNA replication in rat liver cells, also is shown to cause a significant increase in the methylation of chromatin proteins in these cells. This increase in the methylation apppears to correlate with the increase in DNA replication. Specificity of this phenomenon is suggested by its absence in kidney and spleen of the hormone-treated animals, two tissues that also fails to respond proliferatively to the iodothyronine.