Mitochondrial DNA, RNA and protein synthesis in normal and hypothyroid developing rat liver.

Mitochondrial DNA, RNA and protein synthesis in normal and hypothyroid rat liver between the ages of -3 and 21 days were followed. In normal rats DNA polymerase activity and protein synthesis behaved similarly, showing two peaks of activity, one at -3 and the other at 21 days of age. RNA polymerase activity did not change between days -3 and 14, whereas it increased by 21 days of age. Hypothyroidism delayed the developmental pattern of DNA polymerase activity, affected RNA polymerase activity only at 21 days, whereas it inhibited protein synthesis at birth and in the third week of life. The cytochrome aa3 content appeared to be affected by hypothyroidism at birth and at 21 days of age.