Gastrin reverses established cholangiocyte proliferation and enhanced secretin‐stimulated ductal secretion of BDL rats by activation of apoptosis through increased expression of Ca2+‐dependent PKC isoforms

Abstract: We posed these questions: (i) Does administration of gastrin to 1‐week bile duct ligation (BDL) rats inhibits established cholangiocyte proliferation and ductal secretion? (ii) Is gastrin inhibition of cholangiocyte proliferation and secretion of BDL rats associated with enhanced apoptosis? (iii) Are gastrin's effects on cholangiocyte function associated with increased expression of protein kinase C (PKC) isoforms; and (iv) Is gastrin stimulation of cholangiocyte apoptosis regulated by the Ca²⁺‐dependent PKC pathway? Methods: Seven days after BDL, rats were treated with gastrin by minipumps for 14 days. Cholangiocyte proliferation was assessed by measurement of the number of PCNA and CK‐19 positive cholangiocytes in sections, and PCNA expression in cholangiocytes. Ductal secretion was determined by measurement of secretin‐induced cAMP levels and choleresis. Apoptosis was evaluated by TUNEL analysis in sections and annexin‐V staining in cholangiocytes. The expression of PKC isoforms was determined by immunoblots. Results: Gastrin inhibits established cholangiocyte proliferation and enhanced secretin‐stimulated ductal secretion of BDL rats. Gastrin's effects on cholangiocyte function were associated with enhanced apoptosis and increased expression of PKC alpha, and beta I and II. Gastrin increases in cholangiocyte apoptosis were blocked by BAPTA/AM and H7. Summary/conclusion: Gastrin inhibits cholangiocyte proliferation and secretin‐induced ductal secretion in BDL rats by increasing apoptosis through a PKC‐mediated mechanism.