Age-related changes in the rates of polypeptide chain elongation

The time of an average polypeptide chain synthesis, ts, in the liver and brain cortex of rats of various age--from the 17th day of prenatal life up to the 24th month of the postnatal period--was estimated. At the end of the prenatal period the value of t is much higher than in postnatal life. In newborns, the t value is minimal, showing a gradual increase during the postnatal development. Determination of an average molecular mass of newly synthesized polypeptides demonstrated that the increase of t in postnatal life is due to the decrease of the rate of polypeptide chain elongation.