Gastric lipase in the newborn rat.

A substantial portion of rat milk triglycerides was hydrolyzed in the ligated stomach of suckling rats with excised lingual gland and pancreas, due to the action of gastric lipase. Free fatty acids were the main lipolytic products. There were some diglycerides and traces of monoglycerides. Medium chain length (C8-C12) fatty acids were predominantly recovered in the free fatty acid fraction, whereas the remaining tri- and diglycerides became richer in long chain (greater than or equal to C14) fatty acids suggesting a preferential lipolysis of medium chain fatty acid ester bonds. The lipase activity in extracts of stomach wall and sublingual gland tissue was more stable at acid pH and more resistant to the action of pepsin than the activity of pancreatic lipase. Trypsin strongly affected lingual lipase activity but only moderately reduced gastric and pancreatic lipase activity. Presence of sodium taurocholate made the lingual and gastric lipases less sensitive to proteolytic attack. It was also found that the activity of gastric lipase, related to the tissue protein content, decreased with the age of rats, whereas that of lingual lipase increased. The joint capacity of the stomach and lingual gland lipases amounted to about 50% of the total digestive lipolytic capacity 6 days after rat birth but decreased to about 20% at 60 days of life. This was due mainly to the considerable increase in the pancreatic gland size.