Intestinal Absorption of C14-Palmitic Acid and C14-Tripalmitin in the Rat

Abstract

C¹⁴-palmitic acid or C¹⁴-tripalmitin has been fed to rats and distribution of the C¹⁴ in various lipids of intestine, of intestinal contents and of liver determined. Mono-, di- and triglyceride as well as free fatty acid fractions of intestinal contents were found to contain C¹⁴ activity during the period of absorption. Most of the activity, however, resided in free fatty acids and triglycerides. At this time the triglycerides of the intestine had the predominant labeling and the mono- and diglycerides had the least. When free palmitic acid was fed much more of the activity was found in the free fatty acid fraction of intestinal contents but considerable activity was also found in diglycerides and triglycerides. Initially, triglycerides of the intestine had the predominant labeling but as absorption proceeded this activity decreased with a concomitant increase in labeling of the phospholipid fraction. Monoglycerides had insignificant C¹⁴ activity at all times. Total C¹⁴ activity measured three hours after feeding either C¹⁴-palmitic acid or C¹⁴-tripalmitin was greater in phospholipids than in triglycerides of hepatic lipids. However, the specific activity of the triglyceride fatty acids was higher than that of phospholipid fatty acids. Small but significant amounts of C¹⁴ were also found in mono- and diglycerides as well as cholesterol esters of hepatic lipids.