Effects of several common long chain fatty acids on the properties and lipid composition of the very low density lipoprotein secreted by the perfused rat liver.

1. Livers from normal fed male rats were perfused in vitro with a bloodless medium which contained intially 3% bovine serum albumin and 100 mg% glucose. Albumin alone, or myristate (14 : 0), palmitate (16 : 0), palmitoleate (16 : 1), stearate (18 : 0), oleate (18 : 1), or linoleate (18:2) was infused at a constant rate (496 mumol/4 h), as a complex with albumin, during the experiment. 2. The very low density lipoprotein secreted by the liver after infusion of unsaturated fatty acids (16 : 1, 18 :1, 18 : 2) has a faster rate-zonal mobility in the ultracentrifuge and is, therefore, probably a larger particle with fewer moles of phospholipid and cholesterol relative to triacyglycerol (triacyglycerol/phospholipids/cholesterol = 100/25.1/16.4) than the very low density lipoproteins produced after infusion of saturated (14 : 0, 16 : 0, 18 : 0) fatty acids (triacyglycerol/phospholipids/cholesterol = 100/30.1/19.1). The molar ratio of phosphoipids/cholesterol of the very low density lipoprotein was similar regardless of which fatty acid was infused. The predominant fatty acid of the very low density lipoprotein or hepatic triacyglycerol, in all cases, was the infused acid. 3. We conclude that free fatty acid regulates the quantity and proportions of triacyglycerol, phospholipids, and cholesterol secreted by the liver in the very low density lipoprotein, and therefore, may secondarily influence concentrations of lipids in the very low density lipoprotein and other plasma lipoproteins circulating in vivo.