Activity of Peptide Hydrolases in Epithelial and Subepithelial Layers of Small Intestine of Rats of Different Age after Protein Deprivation

A significant decrease of protein content in epithelial, stromal, and muscular-serosal layers of jejunum and ileum, especially in aged animals, is revealed in rats of different age groups (young, mature, aged) after 10-day-long protein deprivation. The responses of peptide hydrolases (aminopeptidase M and glycylleucine dipeptidase) were different. There were, as a rule, no changes of these enzyme activities in small intestine of young rats, except for decreased activity of aminopeptidase M in stromal layer of jejunum and increased activity of both peptide hydrolases in epithelial layer of ileum. In mature animals, increased activities of these enzymes also was observed in the epithelial layer of jejunum and ileum and in the stromal layer of ileum in comparison with the rats receiving a full-value nutrition. In aged rats, a much more pronounced rise of these enzyme activities in the layers of small intestine was revealed after protein starvation in comparison with young and mature rats. Probably, such increase of the peptide hydrolase activities in the layers of small intestine after protein deprivation can be considered as an adaptive-protective reaction of the organism in response to formation of significant amounts of low-molecular peptides as a result of protein catabolism