The ductular cell reaction of rat liver in extrahepatic cholestasis: I. Proliferated biliary epithelial cells

Abstract

The ductular cell reaction in the liver of rats during the second to sixth weeks following ligation of the common bile duct is in part an organized proliferation of ductular (biliary epithelial) cells. The cells show an invariable tendency to surround lumina. Thin ( I 2μ ) sections exmined in the light microscope assist in the understanding of the behavior of ductular cells since the lumina of the penultimate bile-conduction channels can be more clearly visualized than in routine sections. Biliary epithelial cells from proliferated ductules in rats killed two to six weeks after the ligation, show by electron microscopy a persistence of some of the changes noted as occurring during the first 14 days of their proliferation, a paucity of microvilli, edema of microvilli, an increase of the endoplasmic reticulum, and an increase of free ribosomes. Additional abnormalities develop in ductular cells after day 14 of cholestasis. The Golgi zones multiply and become prominent. Smooth-surfaced vesicles increase in number. Some cells become increasingly electron-opaque, and have been designated as ‘dark’ cells. Other cells may acquire a unique one-centriole type of cilia which have an abnormal 7 + 1 doublet filament arrangement. The functional effectiveness of these cilia could not be assessed, owing to the absence of information about any other comparable cilia with a known motility. It was suggested that the prominent ER and RNP granules may signify an increased protein production by proliferating cells rather than evidence of elaboration of a protein-rich secretion. The prominence of Golgi zones and of smooth-surfaced vesicles was interpreted as possible evidence of secretory activity involving water and electrolytes. ‘Dark’ biliary epithelial cells may form as a result of a sudden discharge of such secretion into ductular lumina.