[Modulation of the rate of mRNA poly(A)-segment shortening during embryonal and postnatal development].

A procedure for determination of the rate of poly(A) degradation based on a comparative analysis of poly(A)-segments of impulse-labelled mRNA under conditions of subsequent blocking of poly(A) synthesis by cordycepin was developed. The method described was used to analyze the rate of shorting of the poly(A)-segment of mRNA in the liver and brain cortex of the rat during the embryonic and postnatal development. It was shown that throughout ontogenesis the rate of poly(A) degradation in liver cells is significantly higher than in brain cortex cells for both types of polyribosomal mRNAs, the rate of poly(A) degradation within free polyribosomal mRNA being higher as compared to the membrane-bound mRNA for both tissues. On the 17th embryonic day the rate of poly(A) degradation is high in both polyribosomal types; it is decreased by the moment of birth and is either increased in the postnatal life or remains unchanged (free polyribosomes of the liver and membrane-bound polyribosomes of brain cortex).