INHIBITION OF LIPID-SYNTHESIS AND SECRETION IN LONG-TERM CULTURES OF ADULT-RAT HEPATOCYTES BY ALPHA-ASARONE

In this work we studied the effect of alpha-asarone, a hypolipidemic active principle of Guatteria gaumeri Greenman, on hepatic lipid metabolism using adult rat hepatocytes cultured on a feeder layer of 3T3 cells. These cultures synthesize and secrete for at least two weeks various lipids from [C-14]-acetic and [C-14]-oleic acid. Exposure for one or two weeks to 10 mug/ml of a-asarone decreased the secretion of various lipids to the culture medium; triacylglycerol secretion was inhibited by 80-97 %, phospholipid secretion by 70-87 %, cholesterol by 64-70 %, and cholesterol esters by 50-92 %. The incorporation of [C-14]-acetic acid into cellular lipids decreased by 30-81 % and that of [C-14]-oleic acid into phospholipids by 25-47 % whereas the incorporation of [C-14]-oleic acid into triglycerides and cholesterol esters increased 3.2 fold and by 28-36 %, respectively. Similarly, the activities of glycerol-3-phosphate dehydrogenase and malic enzyme, marker enzymes of glycerolipid and fatty acid synthesis, decreased by 22-50 % and 30-76 %, respectively. Our results show that the exposure of the 3T3-hepatocyte cultures to micromolar concentrations of a-asarone significantly inhibits lipid secretion and probably lipid synthesis. They also suggest that at least part of the hypolipidemic effect could be due to a decrease in the secretion of lipids (i.e., lipoproteins) by the hepatocytes.