A unique lipoprotein profile found in the plasma of cultured Japanese eelAnguilla japonica: very low density lipoprotein, but not high density lipoprotein, is the main component of plasma.

A unique lipoprotein profile was found in the plasma of cultured Japanese eel,Anguilla japonica which accumulated more lipid in its muscle than in its liver. The plasma lipoprotein level of Japanese eels was in excess of 54 mg ml(1), a concentration considered to be hyperlipoproteinemic in relation to other teleosts. The plasma lipoproteins consisted of very low density lipoprotein (VLDL, density (d)<1.006 g ml(1)) low density lipoprotein (LDL, 1.006<d<1.085 g ml(1)), high density lipoprotein 2 (HDL2, 1.085<d<1.100 g ml(1)), and HDL3 (1.100<d<1.210 g ml(1)). VLDL, but not HDL, was the main component in the plasma of Japanese eels, unlike most teleosts where HDL is the main component. An additional lipoprotein, vitellogenin (1.210<d<1.280 g ml(1)), was induced by the injection of estradiol-17ß (E2), but VLDL was the main plasma component even in the E2-treated eels. VLDL was a triacylglycerol (TG)-rich lipoprotein and possessed two apolipoprotein (apo) B-like proteins of molecular weights (Mr) 260K and 230K as main components.LDL, HDL2, and HDL3 were revealed to consist of heterogeneous components by a density gradient ultracentrifugation. LDL was separated into three subclasses of LDL1 (1.030<d<1.038 g ml(1)), LDL2 (1.043<d<1.063 g ml(1)), and LDL3 (1.067<d<1.094 g ml(1)). LDL1 with apo B-like protein of Mr 230K was a TG-rich lipoprotein, while both LDL2 and LDL3 were cholesterol ester-rich lipoproteins with apo A-I-and A-II-like proteins of Mr 25K and 14K. The particle sizes of HDL2 and HDL3 subclasses differed, although all of HDL2 and HDL3 subclasses possessed apo A-I-and A-II-like proteins of Mr 25K and 14K as main components. To our knowledge, this is the first report of detailed plasma lipoprotein profile in Japanese eels.