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Free cholesterol
and lecithin (phospholipids) are transferred from cell membranes to pre
B-HDL to form Discoidal HDL. Via lymph this HDL enters the plasma. Through
the action of LCAT (lecithin:cholesterol Acyl Transferase) the Discoidal HDL
becomes spherical and cholesterol is esterified. About 1/3 of the
cholesterol present in HDL is moved to B-100 containing lipoproteins (IDL/LDL/VLDL)
in exchange for TG (2). Cholesterol ester transfer protein mediates
this transfer. The majority of the HDL/cholesterol is internalized by liver
and to a lesser extent by adrenal and gonadal cells via the SR-BI scavenger
protein for use in bile acid and steroid hormone synthesis. |