High-density lipoprotein (HDL) enters cells by unknown means, and the authors of the report speculated that the pathway might involve the SR-B1 receptor. To pursue the possibility, the receptor was transfected (expressed in a cell line that normally did not express lipoprotein receptors), and uptake of radioactive HDL was measured. HDL was rapidly taken up by the cells compared with untransfected cells. Other measurements showed that the lipid (but not the protein) component of HDL was taken up by the cells. The distribution of HDL lipid in the HDL-expressing cells was found to be different from the distribution of low-density lipoprotein (LDL) lipid in other cells that expressed the LDL receptor, suggesting, the authors reasoned, that the cellular pathway by which the SR-B1 receptor delivered lipid differed from the pathway by which the LDL receptor delivered lipid. The authors detected SR-B1 in the cells of several tissues in the body where, they suggested, the receptor plays a role similar to that in the model cell system studied.