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.

Abstract

Summary.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.The majority of recent electron microscope studies on the hepatic sinusoidal cells (nonparenchymal cells) have been carried out in rat or mouse livers. Among rodents, however, hepatic sinusoidal cells have been known to vary ultrastructurally from species to species as recently shown by LEEUW et al. (1982b) in their comparative morphological, peroxidase-cytochemical and experimental (latex-bead endocytosis) studies on the Kupff er and endothelial cells in the rat and mouse.Thus, they strongly precautioned against the careless application of rat liver data to other species. The results in vivo obtained by LEEUW et al. (1982b) have further been confirmed by MONTECINO-RODRIGUEZ et al. (1982) in their peroxidase cytochemical study of isolated and cultured Kupffer and endothelial cells from rat and mouse liver. Also the fatstoring cell of Ito is known to show considerable species differences.The light microscopic studies by ITo and his collaborators have revealed that the fat-storing cell in 359

Stratified laminae fenestratae (alveolus fenestratus endothelialis) in the glomerular capillaries of the mouse kidney.

“…The structural details of the alveolus fenestratus endothelialis of the normal mouse kidney in the present study is basically the same as the simple two or three fold stratified laminae fenestratae in normal rats, guinea pigs and rabbits already reported by others (WOLFF and MERKER,1966;YOSHINARI and FUJITA, 1982;NOZAKI and MIY0SH1, 1984;OHATA et al, 1984;FUJITA and MIYOSHI, 1985), although, the frequency and development of the structure are much more extensive in mice. This constant appearance, regardless of species difference, suggests that the alveolus fenestratus is not an artifact but represents some general and fundamental feature of the fenestrated endothelial cell.…”

“…This structure is assumed to represent a `small pore system' proposed by physiologists in relation to the transendothelial transport mechanism (LANDIS and PAPPENHEIMER,1963). However, the occasional occurrence of the stratified lamina f enestrata has been reported in the glomerular capillary of both the rat and rabbit kidney (WOLFF and MERKER, 1966;YOSHINARI and FUJITA, 1982;FUJITA and MIYOSHI, 1985), and in the sinusoidal endothelium of the liver and adrenal cortex of monkeys and guinea pigs (NOZAKI and MIYOSHI, 1984;OHATA et al, 1984). Furthermore, the lamina fenestrata has been described as occurring even on the thickened perikaryal portions of the glomerular endothelium of the kidney, designated as pored domes (YOSHINARI and FUJITA, 1982).…”

A transmission electron microscopic study of rabbit liver sinusoids with special remarks on an experimentally induced canalicular system and the "pored domes" in the endothelial cells.

“…In our previous transmission electron microscopic (TEM) study on the sinusoidal cells of guinea pig livers (OHATA et al, 1984), we demonstrated a meandering canalicular system in the thicker portion of the cytoplasmic extension and in the perikaryonal cytoplasm of the endothelial cell. In addition, the "pored domes", as first revealed by FUJITA and his collaborators (FUJITA et al, 1976;Y0sHINARI and FUJITA, 1982) by scanning electron microscopy (SEM) in the glomerular endothelial cells of the rat and rabbit kidney, were also found in the sinusoidal endothelial perikaryon of guinea pig livers.…”

Electron microscopy of fat-storing cells in liver diseases with special reference to cilia and cytoplasmic cholesterol crystals.

“…The single cilium of fat-storing cells in the human liver was first reported by ITO and SHIBASAKI (1968) and later by many authors in other vertebrates (WAKE, 1971;YAMA-MOTO and ENZAN, 1975;TANUMA and ITO,1978;TANUMA et al, 1981;OHATA et al, 1982aOHATA et al, , 1984DE LEEUW et al, 1984). Its axonemal structure, however, has not been demonstrated because it is rarely encountered under the electron microscope.…”

“…Therefore, the cilia of these cells are probably immotile, and likely play a role as a sensory or chemical receptor as such cilia are assumed to do in other types of cells (CURRIE and WHEATLEY,1966;OHATA et al, 1982b). Other authors have made the same assumption about the cilia of fat-storing cells (TANUMA et al, 1981;OHATA et al, 1984), although they could not demonstrate the axonemal ultrastructure.…”