Relative contribution of the main tissues and organs to body fatty acid synthesis in the rat.

Tritiated water was used to measure the rate of fatty acid synthesis in the main tissues and organs of 7-week old Wistar male rats in order to determine the relative contribution of each tissue to body fatty acid synthesis. We reached the following conclusions: (a) the liver is the main site of fatty acid synthesis, it alone synthesizes 42% of the newly synthesized fatty acids in the body. (b) The dissectable white adipose tissues synthesize 27% of the fatty acids in the body. This group of tissues is heterogeneous because the mesenteric adipose tissue alone contains 40% of the labeled fatty acids present in the white adipose tissues. (c) Besides the intestines, organs other than the liver play a negligible role (2% of the total) in fatty acid synthesis. (d) The skin contributes 7% of the body fatty acid synthesis. (e) The rest of the carcass, essentially composed of the musculature and the skeleton, contributes 18% of body fatty acid synthesis and accounts for 33% of the extrahepatic tissue fatty acid synthesis.