Fine Structure of Hepatic Parenchymal Cells of the Liver in Jaundiced Patients and Experimental Dogs

Abstract

Fine Structure of hepatic parenchymal cells in jaundice has been dealt with in many studies. Nonetheless, there still remains uncertainty regarding the mechanism of bilirubin metabolism and jaundice.
For the purpose to clarify this problem, hepatic parenchymal cells were observed by electron microscope.
Eight liver biopsy specimens were used for this study. One was from normal dog, and four were from dogs with obstructive jaundice due to ligation of bile duct. Three were from dogs with hyperbilirubinemia induced by intravenous unconjugated bilirubin infusion. In addition to this, human liver biopsy specimens were used. One was from patient with obstructive jaundice due to the carcinoma of the head of pancreas. The others were from the patient with cholestatic jaundice of pregnancy and from the patient with Dubin-Johnson syndrome.
Results of the observation were as follows.
(1) Increase in number of the smooth surfaced endoplasmic reticulum and lysosome.
(2) Increase in width and density of the pericanalicular ectoplasm.
(3) Changes in morphology and number of bile canaliculus.
(4) Changes of intercellular space and surface to neighbouring hepatic parenchymal cells.
At first, lysosomes appeard near the Golgi complex and as they increased in size and density, they were found remotedly from the Golgi complex. Bile canaliculi usually dilated and showed loss of microvill, or stunted microvilli. Moderately or highly electron opaque substance was seen in the lumen. After intravenous injection of bilirubin in dog, number of bile canaliculus increased. Surface to neibouring cells sometimes protruded microvilli or microvilli-like projections into intercellular space and in this space moderately or highly electron opaque substance was seen.
From these results, we concluded as following. Uptake of bilirubin occurs without any morphological changes of sinusoidal surface. Smooth surfaced endoplasmic reticulum plays important role in conjugating and transporting bilirubin. Golgi complex and lysosome transport conjugated bilirubin. Most of bilirubn is excreted into bile canaliculi through pericanalicular ectoplam largely by diffusion without any defect of cell membrane and small amount of bilirubin into intercellular space and space of Disse. To increase capacity for excreting bile, at first, the bile canaliculi wind and dilate, then increase their number by ramifying. Excretion into intercellular space by diffusion and reversed pinocytosis plays an important role for occurence of jaundice.