Trinachartvanit, W.; DeVries, A.L.; Cheng, C.- H. C.: Antifreeze glycoproteins (AFGPs) are secreted into the digestive tract from the pancreas in Antarctic notothenioid fishes.
Pancreatic tissues in teleost fishes are diffuse unlike other vertebrates. In the large Antarctic notothenioid fish Dissostichus mawsoni a small reservoir exists at the terminus of the pancreatic tissue duct system in the tissue surrounding the common bile duct. Freezing-melting point (i.e. antifreeze activity) analyses of pancreatic fluid samples (0.2 ml to 1.0 ml) from this reservoir indicate the presence of high levels of antifreeze protein. Polyacrylamide gel electrophoresis of purified antifreeze from pancreatic fluid shows the presence of the same eight sizes of antifreeze glycoproteins (AFGPs) found in the blood except the large AFGPs 1-5 occur in much lower abundance. The intestinal fluid has a similar AFGP profile as the pancreatic fluid, indicating the intestinal AFGPs came from the pancreatic fluid. The antifreeze activity of the intestinal fluid is higher than that of the pancreatic, indicating that the AFGP concentrations in intestinal fluids are higher than in the pancreatic fluids. Since AFGPs in the intestinal fluid appear to be neither digested nor reabsorbed, the higher AFGP levels in the intestinal fluid are likely due to concentration of AFGPs as digested food and water are absorbed.