Scavenger receptor class B, type I (SR-BI) is the major route for the delivery of high density lipoprotein cholesterol to the steroidogenic pathway in cultured mouse adrenocortical cells

The class B, type I scavenger receptor, SR-EI, binds high density lipoprotein (I-IDL) end mediates the selective uptake of RDL cholesteryl ester (CE) by cultured transfected cells, The high levels of SR-BI expression in steroidogenic cells in vivo and its regulation by tropic hormones provides support for the hypothesis that SR-BI is a physiologically relevant HDL receptor that supplies substrate cholesterol for steroid hormone synthesis. This hypothesis was tested by determining the ability of antibody directed against murine (m) SR-BI to inhibit the selective uptake of HDL CE in Y1-BS1 adrenocortical cells. Anti-mSR-BI IgG inhibited HDL CE-selective uptake by 70% and cell association of RDC particles by 50% in a dose-dependent manner, The secretion of [N-3]steroids derived from HDL containing [H-3]CE was inhibited by 75% by anti-mSR-BI Igc, These results establish mSR-BI as the major route for the selective uptake of HDL CE and the delivery of ADL cholesterol to the steroidogenic pathway in cultured mouse adrenal cells.