Synthesis of cholesterol and fatty acids in foetuses and in mammary glands of pregnant rabbits

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Abstract
The synthesis of cholesterol and fatty acids in the rabbit fetus was demonstrated by the rapid incorporation of deuterium from the body water into these substances and by the utilization of Cl4-labelled acetate for these syntheses. It is concluded that all fetal cholesterol is obtained by synthesis within the body of the fetus, that while the fetal extrahepatic tissues synthesize cholesterol, they do not degrade it, and that the fetal liver synthesizes as well as degrades cholesterol, but the amount degraded is only 50% of the amt. synthesized on the 28th day of pregnancy. Synthesis of both saturated and unsaturated fatty acids in the fetal liver and extrahepatic tissues (embryonal adipose tissue) was demonstrated. The fetal placenta synthesizes all lipids studied, but it also absorbs these from the maternal circulation. The maternal placenta appears metabolically inert, at least towards the end of pregnancy. Since there was no apparent destruction of fat in the fetus, it is inferred that the primary source of energy in the fetus must be carbohydrate and that growth is characterized not so much by increased rate of synthesis as by reduced rate or absence of degradation. The synthesis of cholesterol and fatty acids in the non-lactating mammae of pregnant rabbits was shown.