A UNIQUE LIPOPROTEIN PROFILE FOUND IN THE PLASMA OF CULTURED JAPANESEEEL ANGUILLA-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 Japan ese eel, Anguilla japonica which accumulated more lipid in its muscle than in its liver. The plasma lipoprotein level of Japanese eels was i n excess of 54 mg ml(-1), a concentration considered to be hyperlipopr oteinemic in relation to other teleosts. The plasma lipoproteins consi sted 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 d ensity lipoprotein 2 (HDL(2), 1.085 < d < 1.100 g ml(-1)), and HDL(3) (1.100 < d < 1.210 g ml(-1)). VLDL, but not HDL, was the main componen t in the plasma of Japanese eels, unlike most teleosts where HDL is th e main component. An additional lipoprotein, vitellogenin (1.210 < d < 1.280 g ml(-1)), was induced by the injection of estradiol-17 beta (E (2)), but VLDL was the main plasma component even in the E(2)-treated eels. VLDL was a triacylglycerol (TG)-rich lipoprotein and possessed t wo apolipoprotein (ape) B-like proteins of molecular weights (Mr) 260K and 230K as main components. LDL, HDL(2), and HDL(3) were revealed to consist of heterogeneous components by a density gradient ultracentri fugation. LDL was separated into three subclasses of LDL(1) (1.030 < d < 1.038 g ml(-1)), LDL(2) (1.043 < d < 1.063 g ml(-1)), and LDL(3) (1 .067 < d < 1.094 g ml(-1)). LDL(1) with apo B-like protein of Mr 230K was a TG-rich lipoprotein, while both LDL(2) and LDL(3) were cholester ol ester-rich lipoproteins with apo A-I-and A-II-like proteins of Mr 2 5K and 14K. The particle sizes of HDL(2) and HDL(3) subclasses differe d, although all of HDL(2) and HDL(3) subclasses possessed apo A-I- and A-II-like proteins of Mr 25K and 14K as main components. To our knowl edge, this is the first report of detailed plasma lipoprotein profile in Japanese eels.