586 Biochimica et Biophysics Acta, 486 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHG (1977) 586-589 Q Elsevier/North-Holland Biomedical Press BBA Report BBA 51204 HIGH DENSITY LIPOPROTEIN AND LOW DENSITY LIPOPROTEIN CATABOLISM BY HUMAN LIVER AND PARENCHYMAL AND NON-PARENCHYMAL CELLS FROM RAT LIVER THEO J.C. VAN BERKEL, JOHAN F. KOSTER and WILLEM C. HULSMANN Department of Biochemistry I, Faculty of M edicine, Erasmus University Rotterdam, P.O. Box 1738, Rotterdam (The Netherlands) (Received November 12th, 1976) Summary The capacity of the homogenates from human liver, rat parenchymal cells, rat non-parenchymal cells and total rat liver for the breakdown of human and rat high density lipoprotein (HDL) and human low density lipo- prdtein (LDL) was determined. Human HDL was catabolized by human liver, in contrast to human LDL, the protein degradation of which was low or absent. Human and rat HDL were catabolized by both the rat paren- chymal and non-parenchymal cell homogenates with, on protein base, a lo- times higher activity in the non-parenchymal liver cells. This implies that more than 50% of the total liver capacity for HDL protein degradation is localized in these cell types. Human LDL degradation in the rat could only be detected in the non-parenchymal cell homogenates. These findings are discussed in view of the function of HDL and LDL as carriers for cholesterol. A correlation between high serum cholesterol levels and atherosclerotic heart disease has been clearly demonstrated [ 11. In the blood, cholesterol is carried mainly by low density lipoprotein (LDL) and high density lipopro- tein (HDL). A positive correlation exists between internal lipoprotein cholesterol accumulation and the levels of LDL in the blood [Z] . HDL, however, was found by Berg et al. [3] to be relatively low in the blood of patients with coronary heart disease when compared to normal individuals. Studies concerning the effect of diet and drugs on LDL metabolism in humans indicated that there is a linear correlation between plasma LDL con- centration and its fractional catabolic rate [4]. In a literature survey Levy and Eisenberg [4] concluded that the physiological control of the plasma zyxwvutsrqpon Abbreviations: LDL, low density lipoprotein, density range 1.019-1.063; HDL, high density lipo- Protein. density range 1.063-1.21.