Accumulation of large VLDL in cyclophosphamide treated rabbits. Relationship with lipoprotein lipase deficiency

Rabbit very low density lipoproteins (VLDL) have been fractionated by heparin sepharose chromatography into two subpopulations: an unretained fraction (UR) and a retained fraction (R). The separation profiles of VLDL from cyclophosphamide treated rabbits differed from those obtained in normal animals: UR fraction was far more important in treated rabbits than in control animals. Comparative studies of the two VLDL subfractions isolated from treated rabbits have been performed. Polyacrylamide gel electrophoresis in presence of urea showed a similar distribution in both fractions of apolipoproteins X, a group of low molecular weight apolipoproteins detected after antimitotic therapy. SDS - polyacrylamide electrophoresis revealed the presence of one form of apolipoprotein B: apo B100 in the VLDL from treated rabbits giving evidence of their hepatic origin. Relative to the R-fraction, the UR-fraction was characterized by an increased triacylglycerol content and a larger diameter as observed by electron microscopy. In vitro incubations with lipoprotein lipase and reisolation of postlipolysis particles suggest that both VLDL fractions can undergo metabolic conversion to LDL. A decrease of lipoprotein lipase activity after treatment, as previously observed, may thus explain the accumulation of the large VLDL.