The kinetics and specificity of the interaction of nascent HepG2 LDL w
ith the HepG2 LDL receptor were examined. I-125-Labeled HepG2 LDL and
plasma LDL were bound by HepG2 cells in a specific and saturable manne
r at 4-degrees-C. Competition studies with HepG2 LDL and plasma LDL in
dicated that both ligands bound to the same receptor. Scatchard analys
es of the specific 4-degrees-C-binding data revealed a K(d) of 75 nM f
or HepG2 LDL and a K(d) of 30 nM for plasma LDL suggesting that HepG2
LDL bind less efficiently to the HepG2 LDL receptor than plasma LDL. B
inding, internalization and degradation studies carried out at 37-degr
ees-C indicated that HepG2 cells are capable of catabolizing their own
nascent LDL; however, under normal experimental conditions re-uptake
of nascent LDL is quantitatively insignificant.