Abstract
We have reported H-35 rat hepatoma cell line has different lipoprotein receptors for LDL, chylomicron-remnants (CM-R) and HDL. Aim of the present study was to investigate the effect of lipoprotein deficient serum (LPDS) in medium on regulation of lipoprotein receptors, which was compared to the effect of newborn calf serum (NBCS).
Prior incubation of cells with 15% LPDS for 44 hours increased the maximum amount of LDL and CM-R associated with cells to 1.9±0.3 and 3.9±1.2 fold, respectively, whereas the binding of non-apo E-HDL was increased only 1.0±0.1 fold. Uptake and degradation of 124I-LDL at 37°C were increased to 2.0 fold by LPDS, but those of 125I-HDL2, were increased to 1.3 fold. Binding constants with cells which were determined competitive displacement assays, were studied. Induction of LDL receptor by LPDS resulted in increased numbers of receptors without changes of affinity. HDL2 receptors was not induced and the binding constants of HDL2 also were not changed. Chylomicron-remnant receptor activity was increased by growth in LPDS more than LDL receptor.
The different effects of these experimental perturbations on the binding of the three lipoprotein classes indicate the presence of three separate receptors in the H-35 rat hepatoma cell line.
