A transmission electron microscopic study on sinusoidal cells of guinea pig liver, with special reference to the occurrence of a canalicular system and "pored domes" in the endothelium.

Hepatic sinusoidal cells in the guinea pig were examined by transmission electron microscopy (TEM). A meandering canalicular system was detected in the sinusoidal endothelial cell both in thicker portions of cytoplasmic extensions and in small areas of the perikaryon. It consisted of meandering canaliculi with vacuolar expansions and constrictions, which penetrated the endothelial cytoplasm, forming as a whole a network. The canaliculi possessed more than two openings which usually communicated with the sinusoid, but occasionally poured themselves into the Disse's space. This network of canaliculi seems to permit infiltration of blood plasma. The "pored domes" recorded by Fujita and his collaborators on the glomerular endothelium of the rat and rabbit kidney were also revealed on the perikaryonal cytoplasm of the sinusoidal endothelium of guinea pig liver. Osmium-blackened lipid droplets were found in the sinusoidal endothelium, which suggested the release of lipid into the sinusoid. Short-term administrations of excessive vitamin A exerted no influence on the endothelial lipid droplets. The guinea pig is a rodent species which stores a very small amount of lipid droplets in its fat-storing cells and the so-called empty fat-storing cells were frequently detected. A single cilium was often found in the fat-storing cells in the guinea pig as in other species.