Lipid synthesis in various organs of the rat during postnatal development

The incorporation of 3H2O into the lipids of brown and white adipose tissue (BAT and WAT), skin, liver, heart, kidney, brain and lungs was studied 1 h after injection in rats aged 1, 13 and 22 days. In the younger age group, triglyceride synthesis was considerably higher in BAT than in any other tissue, while in the 22-day-old rats, this is no longer the case. Cholesterol synthesis in the oldest age group was highest in liver. In the younger animals, there was little difference between tissues in the low rate of cholesterol synthesis except in the brain where the rates of all lipid syntheses were highest on day 13. The surprisingly high rate of triglyceride synthesis in BAT of infant rats is partly due to the high rate of synthesis of the glycerol moiety. Nevertheless, on hydrolysis, the rate of fatty acid synthesis was still highest in these animals.