1. Detailed studies have been made of the plasma lipoprotein abnormalities in parenchymal liver disease to test the hypothesis that the abnormalities would correlate with plasma lecithin-cholesterol acyltransferase (LCAT) activity.
2. When LCAT was high, very-low-density-lipo-proteins (VLDL) were normal in composition and had a normal pre-β electrophoretic mobility. When LCAT was low, VLDL concentrations were greatly reduced.
3. With high LCAT low-density lipoproteins (LDL) were normal. The LDL particles found with low LCAT activity were of normal size but of abnormal composition, being triglyceride rich and cholesteryl ester poor. Regardless of LCAT activity LDL were present in normal amounts.
4. High-density lipoproteins (HDL) were normal in composition and electron-microscopic appearance when LCAT activity was high. When LCAT activity was low HDL were abnormal in composition and ‘stacked discs’ were seen on electron microscopy.
5. These results suggest that low LCAT activity may be the cause of at least some of the lipoprotein changes of parenchymal liver disease.