Pancreatic Adaptation to Change in Dietary Protein Source in Rats Fed at Different Frequencies

Abstract

The rates at which the pancreatic concentrations of chymotrypsinogen, trypsinogen, amylase, and nucleic acid adapt to the substitution of whole-egg protein for casein at the 15% level of the diet were determined over a 2-week period using rats fed 1) ad libitum, and 2) for 1-hour intervals spaced 12 hours apart (space-fed). Chymotrypsinogen and trypsinogen increased almost immediately, with maximal adaptation occurring within 2 to 4 days. Four to seven days were required for amylase to adjust, by increasing, to the change in protein source. There was some evidence to indicate that the mechanisms mediating amylase and protease induction were not identical although the direction of adaptation was the same for all 3 enzymes. Enzyme and RNA levels in rats fed the same diet did not differ significantly regardless of feeding frequency on any specific day of the experiment although, on the average, more chymotrypsinogen and trypsinogen, but not amylase, were found throughout the experimental period in rats fed the egg protein diet at intervals. The introduction of whole-egg protein into the diet caused pancreatic RNA but not DNA to increase as much as 66% within 2 to 3 days.