Very low density lipoprotein binding to adipocytes.

Human very low density lipoprotein (VLDL) has been found to interact with both isolated adipocytes and adipocyte membranes in a manner which is saturable, reversible and dependent on time and temperature. Except for a difference in maximum binding capacity, a similar pattern is seen with both rat epididymal adipocytes and human omental adipocytes. The capacity of rat cells is 0.04 micrograms VLDL per 2 x 10(5) cells. For human cells the capacity is 0.321 micrograms VLDL per 2 x 10(5) cells. Scatchard plots of the competition data are linear. This, and dissociation studies conducted in the presence or absence of unlabelled VLDL suggest that there is no cooperative interaction between the binding sites. Unlabelled VLDL and HDL each compete equally with 125I-labelled VLDL for binding sites. LDL is 25 times weaker as a competitor. Intralipid and unrelated peptides have no effect. These data suggest that the ligand is not apolipoprotein B and not apolipoprotein A. The competitive effect of HDL is not dependent on its apolipoprotein E content. A preparation of C apolipoproteins (75% C-11) is as potent as unlabelled VLDL in competing with 125I-labelled VLDL for binding sites. These data indicate that VLDL can bind to adipocytes. The receptor can interact with other lipoproteins. If differs from the LDL receptor as it does not interact with apolipoprotein B or apolipoprotein E, but binds to a C apolipoprotein.