In the direct pathway of HDL returning cholesterol to the liver, which receptor mediates uptake of cholesteryl esters on hepatocytes?

• A. SR-B1 Receptor
• B. LDL Receptor
• C. ABCA-1
• D. LRP

Answer: (A)

The main concept is that delivering cholesterol from HDL to the liver occurs through selective uptake of cholesteryl esters mediated by a specific receptor on hepatocytes. This receptor, SR-B1, binds HDL and allows the cholesteryl esters inside HDL to move into the liver cell while the HDL particle largely stays intact to return to circulation and collect more cholesterol. This direct pathway is different from how LDL delivers cholesterol, which involves internalizing the whole LDL particle via the LDL receptor. ABCA-1 is important for transferring cholesterol out of cells to form nascent HDL, not for HDL picking up cholesteryl esters from HDL itself. LRP has other clearance roles and is not the main receptor for HDL CE uptake by liver.