Effect of the administration of large doses of vitamin A on the fine structure of rat liver with special reference to changes in the fat-storing cell.

Abstract

The fine structural alterations of the liver, especially of three cell types in the hepatic sinusoidal wall, i.e., the endothelial, Kupffer and fat-storing cells, were observed in rats parenterally given excessive doses of vitamin A (25, 000 or 50, 000i.u.) twice a day for four days.In these experimentally hypervitaminotic rats it has been revealed that enlarged sinusoidal cells storing abundant lipid droplets were nothing but fat-storing cells. The fatstoring cells which are distributed within the perisinusoidal space and contain, also under normal conditions, lipid droplets, are thus believed to be the main storage sites of vitamin A in the liver. In the hypervitaminotic state these cells underwent hypertrophy and accumulated, probably by synthesis in their own cytoplasm, large amounts of lipid droplets in order to store the excess vitamin A. Vitamin A storage in Kupffer cells was unlikely because they were lacking in lipid droplets. Nevertheless, these actively phagocytic cells were suggested to be involved in the elevated intrahepatic metabolism induced by hypervitaminosis A, since they underwent strong hypertrophy in hypervitaminotic rats showing enlargement and swelling of their lysosomes. The sinusoidal endothelial cells, which hardly showed any morphological alterations in hypervitaminotic rats, were considered rather as essential wall-forming cells which are quite uninvolved in the intrahepatic vitamin A metabolism.In the hepatocytes of hypervitaminotic rats lipid droplets were increased and the enlarged Golgi complex displayed ultrastructural features suggesting the enhanced lipoproetin secretion of the cells.