Conversion of (U-14C)-glycerol, (2-3H)-glycerol and (1-14C)-palmitate into circulating lipoproteins in the rat.
The in vivo formation of labelled very low density lipoproteins (VLDL) from (U-14C)-glycerol, (2-3H)-glycerol and (1-14C)-palmitate was studied in fed female rats. The rate of disappearance of radioactivity from plasma after the i.v. injection with these tracers was similar for (U-14C)-glycerol and (1-14C)-palmitate. With (2-3H)-glycerol, plasma radioactivity at 10 min was lower than with the other substrates although it did not change thereafter. A certain proportion of radioactivity administered as glycerol appeared in plasma lipids, mainly in the VLDL glyceride glycerol fraction, although when (U-14C)-glycerol was the substrate, a considerable portion also appeared in the esterified fatty acids of these lipoproteins. When using (1-14C)-palmitate, practically all the circulating labelled esterified fatty acids appeared in the VLDL fraction, while the labelled free fatty acids appeared in lipoprotein of higher density, presumable free fatty acid-albumin complexes. This data is discussed in terms of the role of the liver in the rapid, continuous cycling of these substrates to yield VLDL-glycerides for their extrahepatic utilization.
D000818:Animals; D002250:Carbon Radioisotopes; D005260:Female; D005990:Glycerol / Q000008:administration & dosage / Q000378:metabolism*; D007275:Injections, Intravenous; D008079:Lipoproteins, VLDL / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism; D010168:Palmitates / Q000008:administration & dosage / Q000378:metabolism*; D010169:Palmitic Acids / Q000378:metabolism*; D051381:Rats; D014316:Tritium
D002250:Carbon Radioisotopes; D008079:Lipoproteins, VLDL; D010168:Palmitates; D010169:Palmitic Acids; D014316:Tritium; D005990:Glycerol