Oleate stimulates the formation of triglyceride-rich particles containing apoB100-apo(a) in long-term primary cultures of human hepatocytes.

Hepatocytes prepared from normal human liver donors were maintained in a synthetic, nutritionally defined, serum-free medium for up to 60 days with continuous secretion of the major plasma lipoproteins. By Western blot analysis, both cell lysates and culture media contained apo(a), both unbound and bound to apo B100, in varying proportions, dependent on the liver donor. In the medium of cells pulse-labeled for 16 h with [35S]methionine the apo(a)-apoB100 complex was predominantly found in the d < 1.006 g/ml triglyceride-rich particles (TRP). Incubation of the cells with a bovine serum albumin-potassium oleate complex in a molar ratio of 1:4 caused a twofold to threefold increase of the TRP-containing apoB100-apo(a). In the 48 h unlabeled conditioned medium apoB100-apo(a) was distributed among the d < 1.006, d < 1.063 and d < 1.21 g/ml lipoproteins, with a small amount in the d > 1.21 g/ml sedimenting fraction, suggesting that the newly secreted apoB100-apo(a)-containing TRP had undergone remodeling. The results indicate that primary human hepatocyte cultures produce both apo(a) and apoB100-apo(a) and that the latter affiliates preferentially with TRP, forming a lipoprotein complex that is affected by endogenous triglyceride synthesis, and can be metabolically modified in the culture medium of human primary hepatocytes.