Abstract
SummaryOxyntic gland mucosal ribosomes from 7− to 30‐day‐old rats were asayed for their ability to synthesize endogenous messenger RNA (mRNA) and poly(U)‐directed protein in a cell‐free system. Normal rat liver cell sap (105,000 g supernatant) was used as a source for transfer RNA (tRNA) and activating enzymes. Total mucosal DNA and ribosome content [as assessed by ribosomal RNA (rRNA)] were also determined. Although both DNA and rRNA content increased throughout the 4 post‐natal weeks, the rRNA/DNA ratio rose sharply during the 2nd and 4th week after birth. The ability of mucosal polyribosomes to synthesize endogenous mRNA‐directed protein in a cell‐free system remained elevated up to the age of 18 days, then decreased markedly within the next 3 days, and thereafter, declined more slowly. In 21− and 30‐day‐old rats, the rate of endogenous mRNA‐directed protein synthesis by mucosal ribosomes was 50–60% below that of the 7‐day‐old suckling rats. The protein/ polyphenylalanine ratio, which represents a ratio of polysomes to monosomes, was found to be about 57% lower for ribosomes from 30‐day‐old rats as compared to 7‐day‐old suckling animals. The ability of run‐off ribosomes (devoid of endogenous mRNA) to translate poly(U) was also found to be 33% lower for 30‐day‐old rats as compared to the 7‐day‐old suckling animals.
Published Version
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