Abstract
As new nutritional strategies for ruminant are designed to change production efficiency by improving the supply of rumen protect protein, lipid, and even starch, the digestive system must fit to utilize these increased nutrient supplies, especially the pancreas. The objective of this study was to investigate the effects of phenylalanine (Phe) on digestive enzymes synthesis or secretion and cellular signaling in pancreatic acinar (PA) cells of dairy calves. The PA cells isolated from fresh pancreas of dairy calves, and cultured in completed RIPA 1640 medium with no fetal serum but 0, 0.15 and 0.45 mM Phe at 37°C in CO2 incubator for 120 min. The pancreatic tissue segments (PTS) was cut approximately 2 × 2 mm from the fresh pancreas, and incubated in oxygenated Krebs-Ringer bicarbonate (KRB) buffer containing 0 or 0.35 mM Phe at 39°C for 180 min, and the samples were collected every 60 min after incubation. In PA cells, Phe increased (P < 0.05) the α-amylase secretion and mRNA expression, the phosphorylation of ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4EBP1). In PTS, the Phe increased (P < 0.05) α-amylase and trypsin synthesis, secretion and mRNA expression, as well as the phosphorylation of S6K1 and 4EBP1. Conclusively, these results suggested that Phe regulates the synthesis or secretion of α-amylase, trypsin and lipase through mRNA translation initiation factors – S6K1 and 4EBP1.
Highlights
Digestive enzymes are necessary part of the chemical digestion process for animals, and excreted from exocrine glands of cells in the gastrointestinal mucosa [1]
Pancreatic exocrine protein synthesis is needed for production of secreted digestive enzymes, the growth of pancreas, and the replacement of normal cellular components
We found Phe significant increased the synthesis and release of α-amylase in pancreatic acinar (PA) cells and α-amylase, trypsin in pancreatic tissue segments (PTS), but remarkable decreased lipase synthesis in PTS
Summary
Digestive enzymes are necessary part of the chemical digestion process for animals, and excreted from exocrine glands (e.g., salivary gland, pancreas, etc.) of cells in the gastrointestinal mucosa [1]. These enzymes include amylase, lipase, and protease for carbohydrates, fats, and proteins digestion respectively, are produced by pancreatic acinar (PA) cells (pancreatic exocrine cells). Regulation of ruminant pancreatic enzyme synthesis and secretion is an important and worthwhile work for improving both meat and milk yield in ruminant production. Phe has been reported to enhance the synthesis and release of pancreatic enzymes [5,7,8].
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