Metabolism of the lipoprotein secreted by eel hepatocytes cultured primarily.

1.培养的鳗鱼肝细胞合成并分泌唯一一种脂蛋白，即极低密度脂蛋白。鳗鱼血清中含有VLDL和HDL两种主要脂蛋白，但鳗鱼肝细胞不合成和分泌HDL。2. VLDL的特征。(1)VLDL的化学成分。VLDL中鱼藤素、甘油三酯、游离胆固醇、胆固醇酯和磷脂的含量分别为12%、69%、3.6%、0.4%和14%。(2)VLDL的载脂蛋白。VLDL的主要载脂蛋白为载脂蛋白A和B。与哺乳动物肝脏分泌的VLDL最大的不同在于哺乳动物的分泌的VLDL不含有载脂蛋白A作为主要载脂蛋白。(3)VLDL的分泌速率：培养的鳗鱼肝细胞分泌VLDL的速率为3.79 × 1.51 μ g VLDL/mg细胞蛋白/h（n=6）。该值比人肝细胞分泌VLDL的速率高10倍。3.胰岛素和血清脂蛋白的影响。(1)胰岛素的作用。胰岛素抑制VLDL的分泌和14 C-亮氨酸和14 C-乙酸盐掺入VLDL。(2)血清VLDL的影响。当血清VLDL加入到鳗鱼肝细胞中时，肝细胞刺激VLDL的分泌。血清VLDL可刺激VLDL载脂蛋白的合成，尤其是apo B的合成。4.当分泌的VLDL与脂质体或脂蛋白脂肪酶孵育时，形成HDL样颗粒。5.用组织化学方法观察了鳗鱼肌肉中高含量脂质的存在。门静脉注射~（14）C-VLDL后，观察~（14）C-VLDL在肌肉、肝脏、心脏和肾脏中的掺入情况，发现肌肉中的掺入量最高。此外，还发现鳗鱼肌肉细胞质膜上存在与VLDL特异性结合的蛋白质，其分子量为77000。

1. Cultured eel-hepatocytes synthesized and secreted the only one kind of lipoprotein, namely VLDL. Although there are two main lipoproteins in eel serum, VLDL and HDL, eel-hepatocytes did not synthesize and secrete HDL. 2. Characterizations of the VLDL. (1) Chemical composition of the VLDL. The contents of rotein, triacylglycerol, free cholesterol, cholesterol ester and phospholipid in the VLDL were 12, 69, 3.6, 0.4 and 14%, respectively. (2) Apoproteins of the VLDL. Main apoproteins of the VLDL were apo A and B. What is most different from VLDLs secreted by mammalian livers is that the secreted VLDLs of mammals do not contain apo A as a main apoprotein. (3) The rate of the VLDL secretion.Cultured eel-hepatocytes secreted the VLDL at the rate of 3.79*1.51mug VLDL/mg cell protein/h(n=6). This value was 10 times higher than the rates of VLDL secretion by human hepatocytes. 3. Effects of insulin and serum lipoproteins. (1) Effect of insulin. Insulin inhibited the secretion of the VLDL and the incorporation of 14C-leucine and 14C-acetate into the VLDL. (2) Effect of serum VLDL. When serum VLDL was added to the eel-hepatocytes, the hepatocytes stimulated the VLDL secretion. Furthermore, the synthesis of apoproteins of the VLDL, especially apo B, was stimulated by the serum VLDL. 4. When the secreted VLDL was incubated with liposomes or lipoprotein lipase, a HDL-like particle was formed. 5. The presence of high content of lipid in eel muscle was histochemically observed. When the incorporation of 14C-VLDL into the muscle, liver, heart and kidney was investigated after the 14C-VLDL was injected into the portal vein, the incorporation into the muscle was the highest. Furthermore, it was found that there was the protein on the plasma membrane of eel muscle which could bind the VLDL specifically and of which molecular weight was 77,000.