Receptor-mediated binding and degradation of subfractions of human plasma low-density lipoprotein by cultured fibroblasts.
The receptor-mediated metabolism of human plasma low-density lipoprotein (LDL) subfractions was studied. LDL was isolated from healthy donors and further fractionated by density gradient ultracentrifugation into three subfractions: (I) d = 1.031-1.037, (II) d = 1.037-1.041 and (III) d = 1.041-1.047 g/ml, comprising 24 +/- 7%, 46 +/- 8% and 30 +/- 9% of the total LDL protein, respectively. As assessed by electron microscopy and gradient gel electrophoresis, the LDL particle size decreased and the relative protein content increased from fraction I towards fraction III. Fraction II had the highest (Kd 2.6 micrograms/ml) and fraction I the lowest (Kd 5.8 micrograms/ml) binding affinity to LDL receptors of human fibroblasts at 4 degrees C. The rate of receptor-mediated degradation of fraction II was also higher than that of the other two fractions at 37 degrees C. These results suggest that LDL subfractions have different rates of receptor-mediated catabolism depending on particle size or composition, and therefore their metabolic fate and atherogenic properties may also differ.
Jaakkola
O
O
Department of Biomedical Sciences, University of Tampere, Finland.
Solakivi
T
T
Ylä-Herttuala
S
S
Nikkari
T
T
D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000097:blood* / Q000302:isolation & purification; D011973:Receptors, LDL / Q000302:isolation & purification / Q000378:metabolism*
D008077:Lipoproteins, LDL; D011973:Receptors, LDL