A study on vitamin A storage in polar bears in Greenland.

为了探讨维生素A的储存机制，我们对生理上储存了大量维生素A的成年北极熊和北极狐的肝脏进行了研究，采用高效液相色谱(HPLC)、透射电子显微镜(TEM)形态计量学、氯化金染色、检测维生素A自身荧光的荧光显微镜、苏木精-伊红(H&E)染色、马森氏三色染色和石井银染等方法对其进行了研究。高效液相色谱法测定北极熊和北极狐每克肝脏中总视黄醇(视黄醇+视黄酯)的含量为1.8-1.9微摩尔。在北极狐中，视黄酸酯的组成为51.1%棕榈酸酯、26.6%油酸酯、15.4%硬脂酸酯和7%亚油酸酯。经透射电子显微镜观察，北极动物肝星状细胞胞浆内含有大量维生素A脂滴。北极动物肝脏小叶对维生素A的储存呈带状梯度，该梯度为…更多的表现为从肝门周围区域开始，在中间区域达到峰值，向下向肝小叶中央区域倾斜的对称性渐强-渐减轮廓。肝星状细胞的密度(即单位面积的细胞数)在各区带之间基本相同。肝脏中维生素A含量的差异不会改变维生素A酯储存维生素A的梯度和组成。这些结果表明，北极狐和北极熊肝脏星状细胞中维生素A储存能力的异质性是由遗传决定的。2004年7月至8月，我们还在格陵兰岛东海岸的Ittoqqortoormiit捕获了4只北极熊。用形态学方法对肝星状细胞内的脂滴进行分析。随着年龄的增长，液滴的大小和数量增加，这表明维生素是按时间顺序积累的。这一结果表明维生素A从食物中积累并储存在肝星状细胞中。较少

To investigate the storage mechanisms of vitamin A, we examined the liver of adult polar bears and arctic foxes, which physiologically store a large amount of vitamin A, by high-performance liquid chromatography (HPLC), transmission electron microscopy (TEM) morphometry, gold chloride staining, fluorescence microscopy for detection of autofluorescence of vitamin A, staining with hematoxylin-eosin (H&E), Masson's trichrome, and Ishii-Ishii's silver impregnation. HPLC revealed that polar bears and arctic foxes contained 1.8-1.9 micro mole total retinol (retinol plus retinyl esters) per gram liver. In the arctic foxes, the composition of the retinyl esters was found to be 51.1 % palmitate, 26.6 % oleate,15.4 % stearate, and 7% linoleate. The hepatic stellate cells of the arctic animals were demonstrated by TEM to contain the bulk of the vitamin A lipid droplets in their cytoplasm. The liver lobules of the arctic animals showed a zonal gradient in the storage of vitamin A. The gradient was … More expressed as a symmetric crescendo-decrescendo profile starting at the periportal zone, peaking at the middle zone, and sloping down toward the central zone in the liver lobule. The density (namely, cell number per area) of hepatic stellate cells was essentially the same among the zones. The gradient and composition of the vitamin A esters in storing vitamin A were not changed by differences in the vitamin A amount in the livers. These results indicate that the heterogeneity of vitamin A-storage capacity in hepatic stellate cells of arctic foxes and polar bears is genetically determined. We also caught 4 polar bears in Ittoqqortoormiit, in the east coast of Greenland from July through August, 2004. We analyzed the lipid droplets in the hepatic stellate cells by morphological methods. The size and number of the droplets increased due to the aging; this showed the vitamin was accumulated chronologically. This result showed that the vitamin A was accumulated from the food and stored in the hepatic stellate cells. Less