Studies on Eel Liver Functions Using Perfused Liver and Primary Cultured Hepatocytes

Perfused eel livers, isolated eel hepatocytes, and cultured eel hepatocytes are used to investigate eel liver functions such as gluconeogenesis, glycogen synthesis, and lipoprotein synthesis and methods for preparation are described. A novel phosphoenolpyruvate (PEP) synthesis pathway from pyruvate in gluconeogenesis in eel liver was elucidated and PEP synthesis pathways in eel, rat, and pigeon livers were compared. Glycogen synthesis from pyruvate, lactate, and glucose was investigated by using cultured eel hepatocytes. It was found that 10–6 or 10–7 M glucagon didn’t stimulate glycogen degradation in the presence of pyruvate but stimulated glycogen degradation in the presence of lactate. Glycogen synthesis from pyruvate was observed even when 10–6 or 10–7 M glucagon was present. The characteristics of the lipoprotein synthesized and secreted by cultured eel hepatocytes are clarified. Thyroxine and eel serum high-density lipoprotein (HDL) stimulated the lipoprotein synthesis by cultured eel hepatocytes. In the presence of estradiol-17β, eel serum HDL stimulated vitellogenin synthesis in eel hepatocytes. HDL specifically bound to eel hepatocytes and the ligand of HDL receptor in the plasma membrane of eel hepatocytes was identified to be ganglioside GM4 of eel serum HDL.