Lipids of cultured hepatoma cells: VIII. Utilization of D-[1-14C] glucose for lipid biosynthesis

Abstract

Minimal deviation hepatoma 7288C cells (HTC) were incubated in serum-supplemented and serum-free Swim's 77 medium in the presence of D-[1-14C] glucose for 1, 2, 4, 8, 12 and 24 hr. Glucose oxidation to CO2, incorporation into total cell mass, and incorporation into cell and medium lipids were determined. The percentage distribution of total cell lipid radioactivity in individual neutral and polar lipid classes was followed as a function of time. Degradation studies of individual lipid classes were performed to ascertain the percentage of radioactivity in acyl and glycerol moieties. The percentage of D-[1-14C] glucose oxidized to 14CO2, incorporated into cell matter and cell lipids was elevated in cells incubated in serum-free medium as opposed to serum-supplemented medium. The percentage distribution of total cell lipid radioactivity into individual neutral lipid classes from both serum-free and serum-supplemented cultures was as follows: sterols greater than triglycerides greater than free fatty acids greater than sterol esters. The percentage distribution of total cell lipid radioactivity into individual polar lipid classes of serum-supplemented cultures was as follows: phosphatidylcholine greater than phosphatidylinositol greater than sphingomyelin greater than phosphatidylethanolamine greater than phosphatidylserine. The distribution of glucose radiolabel into individual polar lipid classes of serum-free HTC cells was different from their serum-supplemented counterparts: sphingomyelin greater than phosphatidylcholine greater than phosphatidylinositol greater than phosphatidylethanolamine greater than phosphatidylserine. Glycerol from glyceride classes contained a higher percentage of radioactivity than the acyl moieties, with this percentage significantly elevated in serum-free cultures. The data indicate that, although glucose is a substrate for HTC cell lipids, other precursors present in the culture system also contribute to the lipid constituency of this hepatoma cell line.