Ultrastructure of Fenestrated Cells in the Sinusoidal Wall of Rat Liver after Perfusion Fixation

Abstract

Electron microscopic study of the sinusoidal wall was made on the rat liver fixed by perfusion with glutaraldehyde. The majority of sinusoidal lining cells could be divided into two groups; endothelial cells and Kupffer cells. The former appeared general wall-forming cells, while the latter frequently protruded into the sinusoidal lumen, exhibiting intense phagocytic activity. The endothelial calls possessed numerous pores in their attenuated part of the cytoplasmic processes, forming a sieve plate-like structure as described by Wisse. Additional findings also suggested the actual exchange of the materials including the lipoprotein through these pores. On the contrary, there was no elaborate fenestration in the cytoplasm of Kupffer cells. But, a small number of cells, which showed abundant lysosomes, protuberant cytoplasm and fenestrated cytoplasmic processes, exhibited the transitional features between the endothelial cell and the Kupffer cell.