Regulation of pancreatic duct epithelial growth in vitro

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Abstract
Effects of a number of possible trophic factors on growth of guinea pig pancreatic duct epithelial monolayers were investigated. Isolated fragments of main and interlobular ducts were prepared and explanted onto both tissue culture plastic and thick gels of type I collagen. Monolayers growing out from explants were first cultured in a basal medium for 3 or 4 days. Next, the medium was supplemented individually with bombesin, carbachol, caerulein, epidermal growth factor (EGF), secretin, 12-O-tetradecanoylphorbol 13-acetate (TPA), or vasoactive intestinal peptide (VIP). Cells were cultured in the absence or presence of these possible trophic factors, and monolayer areas were determined morphometrically at 0, 2, and 4 days. Rate of growth was determined from increase in area over each 2-day period. Monolayers grown in basal medium alone on plastic increased to 479% of initial area over the 4-day test period; those grown on collagen increased to 523%. Explants cultured in presence of bombesin, carbachol, caerulein, secretin, TPA, and VIP on either substrate grew at rates not significantly different from those cultured in basal medium. By contrast, duct monolayers grown on plastic or collagen in presence of 10 nM EGF expanded in area to 722 and 1,070%, respectively, of their initial areas. The EC50 for this trophic effect was approximately 1 nM. These results show that EGF exerts a potent trophic effect on guinea pig pancreatic duct cells in vitro but also indicate that cell division in the pancreatic main and interlobular ducts is not regulated by caerulein and related peptide hormones that have been reported to have growth-promoting effects on exocrine pancreas in vivo.

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