Morphological studies on a vitamin A-storing cell and its complex with macrophage observed in mouse pancreatic tissues following excess vitamin A administration.

In this experiment, mouse pancreatic connective tissues were examined following excess vitamin A administration, and a new cell type and a new cell complex were found. In the normal state, several cell species and structures are observed in the intralobular and interlobular connective tissues such as fibroblasts, fixed macrophages (one of mononuclear phagocytes), blood capilleries with pericytes, secretory ducts, myelinated or unmyelinated nerve fibers and collagenous fibers. On the other hand, following hypervitaminosis, a special cell type occurred, thatis, a lipid-storing cell. Its lipid droplets might contain vitamin A. This cell is quite similar to the fat-storing cell (Ito's cell) in the liver or vitamin A-storing cell in other tissues, and its lipid droplets revealed a special vitamin A fluorescence under fluorescence microscopy. Thus this cell was named as a "vitamin A-storing cell", and it may be included in the category of the vitamin A-storing cell system (Yamada and Hirosawa, 1976). The localization of this cell is as follows : Some of them were observed randamly in the connective tissues, but others were observed at the periphery of the blood capillaries. The latter was in close contact with the endothelial cells, and surrounded with the thin film of the basal lamina. The origins of these vitamin A-storing cells are of at least two kinds. Some may have originated from fibroblasts (vitamin A-storing cell of fibroblast type) , but others derived from pericytes of the blood capillaries (vitamin A-soring cell of pericyte type) . In the connective tissues of the mouse pancreas following excess vitamin A administration, some activated macrophages were also observed to contain a number of peculiar vacuolar phagosomes, and the cell sometimes showed intimate contact with the vitamin A-storing cell, especially the fibroblast type. The macrophage and vitamin A-storing cell formed a complex, which the authors tentatively named a "phagocyte and vitamin A-storing cell complex". The significances of the vitamin A-storing cells and the complex is also discussed.