Alpha-tocopherol is secreted from rat liver in very low density lipoproteins.
Alpha-tocopherol is secreted from rat liver in very low density lipoproteins.
复制标题
α-生育酚以极低密度脂蛋白的形式从大鼠肝脏分泌。
作者：
W. Cohn;F. Loechleiter;F. Weber
为了验证大鼠肝脏在极低密度脂蛋白（VLDL）中分泌维生素E （α -生育酚）的假设，进行了三项独立的研究。i)当Triton WR-1339阻断血浆乳糜颗粒（CM）和VLDL的清除时，两类富含三酰甘油的脂蛋白中α -生育酚浓度随时间线性增加，尽管VLDL的积累率超过CM。对于禁食的大鼠，VLDL中α -生育酚的出现率略有降低。Triton WR-1339给药后VLDL部分α -生育酚和甘油三酯呈坐标升高。与血清中的情况相反，注射Triton后肝脏中的α -生育酚浓度降低。ii)为了抑制含载脂蛋白B （apoB）的肝脏脂蛋白的分泌，给大鼠喂食含有山茱萸酸的饲料。这导致血清和VLDL中载脂蛋白ob和α -生育酚浓度降低，而肝脏中维生素E含量增加。iii)在肝细胞原代培养中，α -生育酚主要在VLDL内分泌到培养基中。因此，我们得出结论，肝脏在VLDL内分泌α -生育酚，并以这种方式有助于维持血清维生素E浓度。
Three separate studies were carried out to test the hypothesis that rat liver secretes vitamin E (alpha-tocopherol) within very low density lipoproteins (VLDL). i) When the clearance of plasma chylomicrons (CM) and VLDL was blocked by the administration of Triton WR-1339, alpha-tocopherol concentrations increased linearly with time in both classes of triacylglycerol-rich lipoproteins, although accumulation rates within VLDL exceeded those within CM. For fasted rats, appearance of alpha-tocopherol in VLDL persisted at slightly reduced rates. alpha-Tocopherol and triglycerides in the VLDL fraction responded to Triton WR-1339 administration by coordinate increases. In contrast to the situation in serum, alpha-tocopherol concentrations decreased in the liver following injection of Triton. ii) In order to inhibit the secretion of hepatic lipoproteins containing apolipoprotein B (apoB), rats were fed a diet containing orotic acid. This resulted in a reduction of apoB and alpha-tocopherol concentrations in serum and VLDL, whereas the vitamin E content of liver was increased. iii) In primary cultures of hepatocytes, alpha-tocopherol was secreted into the culture media predominantly within VLDL. We, therefore, conclude that the liver secretes alpha-tocopherol within VLDL and in this way contributes to the maintenance of serum vitamin E concentrations.