Changes in the lipid content of rat lymph after the ingestion of [14C] long-chain fatty acids.

Rats were orally administered separately one dose of three labelled long-chain fatty acids: [1-14C] oleic, [1-14C] palmitic or [1-14C] stearic. Samples of lymph were obtained from previously cannulated thoracic ducts and analyzed for the composition and content of labelled fatty acids. Most of the newly recovered and labelled fatty acids were qualitatively and quantitatively similar regardless of which 14C-fatty acid had been administered. Over 20% of the administered fat were interconverted in six hours. The results suggest that the mucosa of the small intestine, the first sites of fatty acid absorption, is also one of the sites of various metabolic processes such as beta oxidation and synthesis which are responsible for some of the changes observed. These processes indicated that by shortening or lengthening the fatty acid composition, the content of the lymph became approximately the same regardless of the precursor fatty acid. The intestinal mucosa became the first tissue to help maintain lipid homeostasis in the rat.