Acute carbon tetrachloride feeding selectively damages large, but not small, cholangiocytes from normal rat liver

The aim of this study was to develop a model of selective duct damage restr icted to hormone-responsive segments corresponding to the ducts damaged in primary biliary cirrhosis (PBC). Carbon tetrachloride (CCl4) was fed by gav age to rats, and 2, 7, 14, and 28 days later, small and large cholangiocyte s were isolated. Apoptosis was determined in situ by morphology and in puri fied cholangiocytes by assessment of nuclear fragmentation by 4,6-diamidino -2-phenylindole (DAPI) staining. Cholangiocyte proliferation was evaluated in situ by morphometry of liver sections stained for cytokeratin-19 (CK-19) and by proliferating cellular nuclear antigen (PCNA) staining in liver sec tions and in purified cholangiocytes by PCNA gene expression. Ductal secret ion was assessed by measurement of secretin receptor (SR) gene expression a nd secretin-induced cyclic adenosine 3',5'-monophosphate (cAMP) synthesis a nd secretin-induced choleresis. Two days after CCl4 administration, there w as an increased number of small ducts, but a reduction of large ducts. Apop tosis, observed only in large ducts, was associated with decreased DNA synt hesis and ductal secretion. Conversely, small cholangiocytes expressed ne n ovo the SR gene and secretin-stimulated cAMP synthesis 2 days after CCl4 tr eatment. Proliferation of large cholangiocytes was delayed until 7 days, wh ich was associated with a transient increase in ductal secretion in vivo. C Cl4 effects on cholangiocytes were reversed by day 28. CCl4 treatment cause s a decrease in large duct mass as a result of a higher rate of apoptosis a nd absence of initial proliferation in large cholangiocytes. These processe s were concomitant with a decrease of ductal secretion in large cholangiocy tes. Small cholangiocytes appear resistant to CCl4-induced apoptosis, and p roliferate and transiently compensate for loss of proliferative and secreto ry activity of large cholangiocytes.