Abstract
Isolated livers from Japanese monkeys were perfused in order to assess the nature of apolipoprotein A-I secreted directly by the liver and to determine the effect of cholesterol feeding on the production of apolipoprotein A-I and on the apo A-I isoprotein pattern. Perfusate containing 3H-leucine was recirculated for 60 min, followed by additional 2 hours perfusion with fresh perfusate. Cholesterol feeding resulted in an increase in serum cholesterol level and in an decrease in HDL-cholesterol. Regression analysis between the serum cholesterol and HDL-cholesterol levels revealed the negative correlation (r=-0.72). Hepatic production of apo-HDL, however, was increased by the cholesterol feeding. In order to assess the nature of apo A-I secreted by the liver, two dimensional electrophoresis of apo A-I was employed. The control perfusate HDL contained isoprotein 2 (basic and immature apo A-I) and 4 (mature one) present in roughly equivalent amounts. On the other hand cholesterol feeding resulted in an increase in basic apo A-I of perfusate HDL. These observations indicate that cholesterol feeding may increase in the catabolism of HDL, which may be dependent on the conversion of proapo A-I to mature apo A-I.
