Receptor-mediated uptake of homologous low-density lipoproteins by isolated liver parenchymal cells of fetal rats.
The binding and uptake of gold-labeled homologous, apolipoprotein E-free low-density lipoproteins (LDL) by isolated fetal rat liver parenchymal cells in suspension were studied ultrastructurally and morphometrically. Binding experiments using 125I-labeled LDL were also performed. After a 2-h preincubation in a lipoprotein-free medium and a subsequent 1-h postincubation in the presence of LDL-gold, fetal liver parenchymal cells exhibit a binding of 248 +/- 17 gold conjugates/100 micron plasma membrane and an uptake of 235 +/- 17 gold conjugates/100 micron2 cytoplasm. Compared with values obtained from freshly isolated non-preincubated cells, these data correspond to a 15-fold and an 18-fold increase in total binding and uptake of LDL-gold, respectively. Competition experiments reveal that this increase is mainly a result of a 23-fold stimulation of specific binding and a 44-fold stimulation of receptor-mediated uptake of LDL-gold. The 125I-LDL binding experiments give a Kd value of 6.3 X 10(-8) M and a maximum binding capacity of 17.3 fmol LDL/10(6) cells. Our data provide evidence, further to our in vivo studies, that fetal rat liver parenchymal cells possess high-affinity binding sites for native homologous apolipoprotein E-free LDL. These sites may correspond to B, E receptors of adult rat liver parenchymal cells.
Dürer
U
U
Institute of Pathological Biochemistry, Friedrich Schiller University, Jena, German Democratic Republic.
Sommer
M
M
Franke
H
H
Schlag
B
B
Dargel
R
R
D000818:Animals; D005333:Fetus / Q000378:metabolism; D006046:Gold; D066298:In Vitro Techniques; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D008854:Microscopy, Electron; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011973:Receptors, LDL / Q000378:metabolism*
D008077:Lipoproteins, LDL; D011973:Receptors, LDL; D006046:Gold