DUCTULAR REACTION AT THE EARLY AND LATE STAGES OF BILIARY OBSTRUCTION: IS THE MECHANISM THE SAME?

Ductular reaction (DR) is one of the classical features of biliary obstruction in humans as well as in experimental models. It is the histological phenomenon expressed by the increased number of ductular profiles (DPs), which is especially intensively studied in rodents' model of common bile duct ligation (CBDL). However, some issues related with DR in long-term CBDL are not clear enough. The liver tissue of male Wistar rats (150-200 g) subjected to CBDL were studied histologically (H&E). The architectonics of the biliary tract was studied by investigation of the corrosion casts obtained by retrograde injection (trough CBD) the solidified mass prepared on the basis of "Protacryl M" widely implemented in orthopedic dentistry. The casts were investigated by electro-optic device ProScope-HR with magnification X10, X50 and X200. DR accompanying CBDO is featured by the development of new DPs, the number of which is permanently increased in association with the prolongation of the terms of Cholestasis. DPs continue to develop in all areas of liver lobules - from portal/periportal region up to the regions containing central veins (hepatic veins tributaries of small calibers). The part of DPs has wide lumens, while the lumens of another part of DPs are hardly notable. In spite of evident ductular metaplasia of hepatic tissue, the small groups of normal by form and structure hepatocytes forming the separate small islets could be revealed. Histological features of these hepatocytes support the proposition that these cells maintain the functional activity on the 4th-5th weeks after CBDO. The results of investigations of biliary corrosion casts on the 4th and 5th weeks of CBDO show that solidifying mass cannot reach the small ducts/ductules and especially bile canaliculi. This fact confirms the interruption of ductular-canalicular junctions (IDCJ). We propose that due to IDCJ the increased pressure in preserved bile canaliculi should stipulate the mitotic activity and biliary trans-differentiation of hepatocytes on the late terms of CBDO and support the generation of ductal-like structures and appearance of new DPs. These ductules generally are not drained into the entire biliary tree.