Effect of Dietary Regimen on Cessation of Uptake of Macromolecules by Piglet Intestinal Epithelium (Closure) and Transport to the Blood

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Abstract
Recent work with absorption demonstrated that neonates nonselectively internalized (“uptake”) macromolecules into intestinal epithelium but differed with respect to the macromolecules subsequently found in the blood (“transport”). The effect of dietary regimens on these separate phenomena was studied. In normal, nursing piglets, and piglets fed automatically 24 times/day, the upper half of the small intestines ceased or had a diminished capacity to internalize macromolecules by 1.5 days of age. The loss in pinocytotic uptake activity (closure) began at the duodenum and proceeded caudally toward the ileum as the piglet aged to about 3 weeks. Three-day-old starved piglets were unaffected in this regard in that they did not have diminished uptake activity (behaving as newborns). Coincident with the loss in uptake activity in the upper small intestines in the fed piglets was a loss in transport capacity by the entire small intestines. Again, starved piglets reacted like newborns and retained transport capacity. This induced loss in uptake of macromolecules was accelerated in piglets in “stressing” dietary situations, i.e., feeding four times/day instead of 24 times and piglets with diarrhea. If closure or cessation of uptake occurred as a result of exposure of intestinal epithelial cells to digestive juices and nutrients then (as it was found) closure would occur first in the duodenum and proceed toward the ileum. Also, any dietary regimen that promoted the flow of digesta into lower parts of the intestine would also promote precocious closure for that area.