Metabolism of chylomicrons and triglyceride emulsions by perfused rat adipose tissue

Abstract

The uptake and metabolism of chylomicrons and artificial emulsions of triglycerides by adipose tissue has been studied in the perfused parametrial fat body of the rat. The triglyceride preparations were labeled with either glyceryl-C14 or with glyceryl-C14 and palmitate-H3. The uptake of both chylomicrons and emulsions was proportional to the blood triglyceride concentration and to the duration of infusion; the uptake of chylomicron triglycerides was about 40% greater than that of the artificial emulsion. About two-thirds of the triglycerides removed were hydrolyzed to glycerol and fatty acids and the rest was retained, without being hydrolyzed, in the fat cells. The uptake and metabolism of triglycerides was greatly reduced when the fat donors were deprived of food for 2 days. About 70% of the fatty acids cleaved from blood triglycerides were incorporated into tissue lipids, whereas less than 15% of those infused as free fatty acids were esterified by the perfused adipose tissue. Labeled glycerol was released to the venous blood for several minutes after the blood stream had been flushed of labeled triglycerides. The findings suggest that a major part of the hydrolysis of blood triglycerides occurred after the triglycerides had been removed from the blood stream.