Biosynthesis of Cholesterol XI. Biosynthesis of Cholesterol and Fatty Acids in Pregnant Rats.

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Abstract
Biosynthesis of cholesterol and fatty acids during the entire course of pregnancy was studied with the help of incorporation of C14 from acetate-1-C14 into these substances in pregnant rats and their fetuses. No appreciable change in rate of biosynthesis in the livers of the pregnant mothers was observed, although total amounts of cholesterol increase with the increase of liver weights during pregnancy and lactation. It is doubtful whether the early embryonal cells produce any cholesterol from acetate but at the end of pregnancy the liver of the fetus synthesizes this substance at least as efficiently as the liver of the mother. Degradation of cholesterol at this time seems to be much less in the fetal liver than in the livers of the normal controls or of the pregnant rats, thus causing a tremendous increase in the apparent incorporation of C14 from acetate- 1-C14 into the fetal liver cholesterol. Only a very minute amount of this substance is transferred through the placenta from the mother to the fetus. At the day of birth gastrointestinal tracts and carcasses accumulate much higher radioactivities in cholesterol of the fetus than in the mothers tissues. Fatty acid synthesis increases in the maternal tissues during pregnancy but reaches a peak only during lactation.