Among the various factors to cause the low serum cholesterol contents of new-borns, which usually amounts only half the value of the maternal level, actove metabolisms in younger animals, together inmature biosynthetic activity could be proposed. The present author, therefor, managed to run a experiment employing Acetate-1-C14 incorporation test in the liver of young rat at its various times after the birth, and obtained results as follows=
The in vitro ineMporatigm of acetate-l-CS into liver cholesterol was traced in new-born rats immediately, 10 days and 2 months after the birth as well as in the maternal adults of those animals. The rate of cholesterol biosynthesis in the liver was 172-245 cpm/g tissue immediately after the bith,r increasing to 728 cpm/g tissue after 2 months. The rate in the maternal adults was 650 cpm/g tissue, a slightly lower value than that of 2 month-old animal, but still higher than that immediately after the birth by over 150%. It seems, therefore, that the difference in the serum cholesterol level between new-born and maternal sides results partly from the difference in the biosynthetic rate of cholesterol in the liver of the animal, as is shown in this study.
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