Effects of Branched Chain Amino Acids on digestive enzymes secretion from pancreas of dairy cows

Abstract

Background : The limited ability of ruminant to digest starch in the small intestine may be attributed to insufficient digestive enzyme activity secreted by the pancreas. The purpose of this study was to investigate effects of leucine (Leu), isoleucine (Ile) and valine (Val) on digestive enzymes secretion from pancreas collected of Holstein dairy cows by tissue incubation in vitro. Methods: Two experiments were designed in the present study. In experiment 1, Five Holstein dairy cows were slaughtered and pancreatic tissue was removed immediately, rinsed with ice-cold normal saline (0.9% Nacl) and cut into small segments (approximately 2 × 2 mm), which were placed in oxygenated Krebs Ringer bicarbonate buffer (KRB) containing no amino acid (control), leu, Ile or Val (2.62, 5.24 or 10.48 mg/mL). Each treatment was repeated for five times and incubated in a 39°C shaker. KRB and pancreatic tissue samples were collected at 60, 120 and 180 min after the incubation. In experiment 2, Five Holstein dairy cows were slaughtered and the pancreatic tissue was immediately removed and treated, which were placed in KRB containing no amino acid (control), leu, Ile or Val (5.24 mg/mL) for incubation 60 min. Results : In experiment 1, The activity of pancreatic α-amylase were increased by Leu ( P < 0.01), Ile ( P < 0.01) or Val ( P = 0.06). Compared with the control group, Leu ( P < 0.05) or Ile ( P < 0.05) could linearly increase the activity of trypsin, but Val ( P > 0.05) had no effect on the trypsin activity. Neither Leu or Val had no influence on the activity of chymotrypsin ( P > 0.05). However, chymotrypsin activity decreased linearly with the increase of the Ile concentration at incubation time 180 min ( P < 0.01). Lipase activity were reduced linearly by Val ( P < 0.05 ). In experiment 2, Leu and Val markedly increased α-amylase activity ( P < 0.05), decreased lipase activity ( P < 0.05). The activities of trypsin and chymotrypsin were not affected by the three amino acids ( P > 0.05), and there was no interaction among them ( P > 0.05). Conclusion: This study demonstrated that Leu, Ile and Val can stimulate the secretion of pancreatic enzymes in vitro, especially α-amylase. There was no interaction between the three amino acids on the activities of α-amylase, trypsin and chymotrypsin.