| Popis: |
Under normal physiological conditions the digestion and absorption of dietary lipids are highly efficiently processed. In humans, the diet generally contains 90 to 120 g of lipids (mostly triacylglycerols), more than 95% of which are absorbed, due to the interplay between the stomach, the small intestine, the liver, and the pancreas (Carey et al., 1983). Several steps can be distinguished in the processing of dietary lipids, including their emulsification, hydrolysis and solubilization, and, last, their uptake into the enterocyte. The emulsification of lipids starts in the stomach and is mediated by physical forces and is facilitated by the partial lipolysis of the dietary lipids (Carey et al., 1983). For a long time, the hydrolysis of dietary triglycerides was thought to begin in the intestinal lumen and to be catalyzed entirely by pancreatic lipase. The stomach was thought to be a transient storage organ, the role of which was limited to mixing lipids with the other nutriments and dispersing them as required. Although many authors observed the occurrence of lipolysis at the preduodenal level in humans and in several other species, the gastric phase of lipolysis was assumed to be negligible and to be of little or no significance in comparison with the intestinal step. Gastric lipolysis was even attributed to pancreatic contamination resulting from a duodeno-gastric reflux. At the beginning of the twentieth century, however, it was observed that gastric juice could hydrolyze fat. In 1901, Volhard stated that gastric lipase was the “ferment” present in gastric juice that was responsible for fat hydrolysis. Finally, the gastric origin of the lipase present in dog gastric juice was established by Hull and Keaton (1917) in dogs with Pavlov stomach under conditions precluding the possibility of any pancreatic contamination. |
