Serum assays for specific radioactivity of cholesterol esters and triglycerides were performed with blood samples drawn from albino rats 3 hours after administration of specified fatty acids and or free cholesterol or cholesterol esters labelled with radioactive C14 upon starvation for 48 hours. The labelled fatty acids used included palmitic acid, stearic acid, oleic acid and linoleic acid. The results may lead to the following conclusions:
1. Cholesterol esters produced in the intestinal wall from dietary cholesterol or from cholesterol originating from ingested cholesterol esters are in limited quantities. Both dietary fatty acids and plasma fatty acids take part in the cholesterol esterification which proceeds in the intestinal wall whereas neither the cholesterol excreted in the intestinal tract nor the plasma cholesterol participates to any remarkable degree in the intramural esterification.
2. In the biosynthetic process of re-esterification of cholesterol derived from dietary cholesterol esters that takes place in the intestinal wall, the fattyacid components of ingested cholesterol esters are replaced with simultaneously administered (dietary) fatty acids.