Abstract
Summary: 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 (≥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.
Speculation: Lingual and gastric lipases are distinct enzymes with a mildly acidic pH optimum. They are stable in acid medium, resistant to peptic proteolysis and able to split all three ester bonds on the glycerol molecule. These properties enable them to efficiently digest milk triglycerides in the stomach of the newborn. There is a carry-over of digestive activity by lingual and gastric lipases into the upper intestine where they supplement the action of pancreatic lipase and complement it with respect to lipid emulsification. Gastric lipase seems important in intestinal lipolysis because since it is activated by bile salts, the presence of which protects the enzyme against tryptic proteolysis. Although the relative contribution of gastric and lingual lipases to the overall lipolytic capacity falls short of that of pancreatic lipase, it is likely that the extrapancreatic lipases are compensatory in conditions of pancreatic lipase deficiency.
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Levy, E., Goldstein, R., Freier, S. et al. Gastric Lipase in the Newborn Rat. Pediatr Res 16 (Suppl 1), 69–74 (1982). https://doi.org/10.1203/00006450-198201001-00014
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DOI: https://doi.org/10.1203/00006450-198201001-00014
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