In Vivo Transformation of Rat Plasma Very Low Density Lipoprotein Into Higher Density Lipoproteins

Summary Following intravenous injection of rat plasma very low density lipoprotein labelled in the peptide moiety with 125 I into rats, there is an early appearance of radioactivity in the protein moiety of both low density lipoprotein and high density lipoprotein fractions. The suggestion that low density lipoprotein and high density lipoprotein are formed from very low density lipoprotein during its delipidation in vivo was investigated by injection of in vitro partially and completely delipidated very low density lipoprotein. The evidence presented shows that very low density lipoprotein and low density lipoprotein can be formed from these labelled peptide fractions and that re‐entry of the very low density lipoprotein peptides into the biosynthetic pathway of plasma lipoproteins probably requires complete delipidation of the lipoproteins.