Lipoprotein metabolism in eel.

鳗鱼、鲤鱼、虹鳟等鱼类的血脂浓度比人类家族性高胆固醇血症和高甘油三酯血症高出数倍，但其原因尚不清楚。鱼类的脂蛋白代谢的研究是为了解决上述问题，因为大部分的血浆脂质是作为脂蛋白的成分存在的。1.本文报道了用本实验室合成的亲脂性荧光染料标记高密度脂蛋白（HDL），研究鳗鱼肝细胞HDL受体。结果表明，鳗鱼肝细胞上存在HDL受体，其Kd值约为20 μ g HDL / ml。此外，HDL刺激肝细胞中脂蛋白的合成和分泌。2.鱼油的一个显著特点是含有较高量的多不饱和脂肪酸，如二十二碳六烯酸（DHA）和二十碳五烯酸。研究了DHA对脂蛋白合成和分泌的影响。DHA促进脂蛋白、三酰甘油和胆固醇的合成，但显著抑制脂蛋白的分泌。3.众所周知，鳗鱼等鱼类的洄游与甲状腺激素有关。研究了T4对脂蛋白合成的影响。T4刺激脂肪生成以及脂蛋白合成。4.比较了从江河洄游到海洋产卵的银鳗和性未成熟的养殖鳗鱼的脂蛋白合成和血清脂蛋白。银鳗肝细胞合成脂蛋白的活性高于鳗鱼肝细胞，且银鳗肝细胞分泌的脂蛋白比鳗鱼肝细胞高。与分泌型脂蛋白相反，银鳗血清脂蛋白的脂质比低于养殖鳗。

Plasma lipid concentration of fishes such as eel, carp and raibowtrout is several times higher than that of familial hypercholesterolemia and hypertriglycemia of human beings, but the reason is unknown. Studies of lipoprotein metabolism in fish are conducted to solve the question described above since most of plasma lipid exist as components of lipoproteins.Four major subjects are studied to investigate lipoprotein metabolism using cultured eel hepatocytes. 1. HDL receptor of eel hepatocytes was investigated using HDL labelled with a lipophilic fluorescent dye, which was synthesized in our laboratory. It was found that HDL receptor existed on eel hepatocytes and the Kd value for HDL was about 20 mug HDL / ml. Furthermore, HDL stimulated a lipoprotein synthesis and secretion in the hepatocytes. 2. It is a remarkable characteristic of fish oil that rather high amount of polyunsaturated fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid is contained in fish oils. Then effect of DHA on lipoprotein synthesis and secretion was investigated. DHA stimulated synthesis of lipoprotein, triacylglycerol and cholesterol, but remarkably inhibited the secretion of lipoprotein. 3. It is known that migration of fishes such as eel has a relationship with thyroid hormone. Effect of T4 on lipoprotein synthesis was investigated. T4 stimulated lipogenesis as well as lipoprotein synthesis. 4. Lipoprotein synthesis and serum lipoproteins of silver eel, which migrates from the river to the sea for spawning, were compared with those of cultured eel, which is sexually immature. Silver eel hepatocytes actively synthesized lipoprotein compared to hepatocytes of cultured eel and the secreted lipoprotein by silver eel hepatocytes had higher ratio of lipid than that by cultured eel hepatocytes. Contrary to secreted lipoprotein, serum lipoproteins of silver eel had lower lipid ratio than those of cultured eel.