Pancreatic reg Gene Expression Is Inhibited During Cellular Differentiation

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Abstract
Background and Objective Factors that control pancreatic regenerating (reg I) gene expression are unknown, but it is believed that its expression may correspond with cellular differentiation. The authors recently demonstrated that reg I is expressed in AR42J, a rat acinar cell line whose state of differentiation can be modulated by dexamethasone. They used this line to study reg I expression during cellular proliferation and differentiation. Methods After treatment of cells with 10 nmol/L dexamethasone, proliferation was assayed by thymidine incorporation; differentiation by expression of elastase I mRNA. Reg I mRNA levels were measured using a rat reg I cDNA probe, and reg I protein levels assayed by enzyme-linked immunosorbent assay of cellular lysates with a polyclonal antibody. The effect of gastrin, cholecystokinin and glucagon on reg I expression was also studied. Results When compared with controls, treatment with dexamethasone caused thymidine incorporation to decrease and elastase mRNA levels to increase. Reg I mRNA decreased from controls of 100 ± 16% to 40 ± 18% (p < 0.05), and reg I protein levels decreased as well. Gastrointestinal hormones had no significant effect on either elastase or reg I gene expression. Conclusions Expression of reg I inversely correlates with the level of cellular differentiation, can be modulated via the glucocorticoid receptor, and is a potential marker of gastrointestinal epithelial differentiation. Despite its presence within a pancreatic acinar cell line, reg I gene expression is not modulated by gastrointestinal hormones.