Hiroo Ito , Minoru Chimata , Megumi Oka , Yasuyuki Suzuki , Natsuko Hamada , Michitaka Fujimaki , Kuniyoshi Oda , Kayoko Fujisawa , Tamio Teramoto , Kazumichi Nakamura , Mitsumasa Nagase , Chikayuki Naito
17 December 2008
The expression of low density lipoprotein (LDL) receptors by cultured rat mesangial cells was demonstrated using immunohistochemical and biochemical methods. Using a mouse monoclonal anti-human LDL receptor antibody, the immunofluorescence technique was applied to cultured mesangial cells and showed granular staining. Immunoblotting analysis of the membrane fraction of cultured mesangial cells showed a single band with a protein of approximately 130,000 molecular weight. In addition, [<sup>125</sup>I]LDL binding and the uptake of [<sup>125</sup>I]LDL by cultured mesangial cells were studied. Binding and uptake both reached an equilibrium after about 30 min of incubation. A 50% reduction in [<sup>125</sup>I]LDL (20 μg protein/ml) binding and uptake occurred when unlabelled LDL was added to cultures at 20-40 μg protein/ml. Addition of high density lipoprotein without apoE to the culture medium did not induce competitive inhibition of [<sup>125</sup>I]LDL binding and uptake by mesangial cells. These findings suggest that cultured mesangial cells have the capacity to express an LDL receptor that regulates the cellular uptake of LDL.