Estrogen-induced increase in uptake of cholesterol-rich very low density lipoproteins in perfused rabbit liver

A nonrecirculating rabbit liver perfusion system was developed to test whether estrogen increases hepatic uptake of radio-iodinated normal and/or cholesterol-rich very low density lipoproteins (VLDL, d < 1.006 g/ml) from cholesterol-fed rabbits. When equal concentrations of VLDL protein from normal rabbits and from cholesterol-fed rabbits were perfused together through the same liver, there was a selectively higher (1.4-fold) uptake of cholesterol-rich VLDL. These particles were rich in apolipoprotein E, and the radioactivity bound to this apolipoprotein was selectively removed by the perfused normal rabbit liver relative to its uptake of apolipoproteins B and C. When livers from estrogen-treated rabbits were perfused under identical conditions as normal livers and with the same lipoproteins, the uptake of cholesterol-rich VLDL was increased by 76%, compared with 21% for normal VLDL.