In the present study, we aimed to evaluate the effect of aging on the absorption of small peptides in spontaneously hypertensive rats (SHRs). Three kinds of dipeptides, glycyl-sarcosine (Gly-Sar), Trp-His, and captopril (a dipeptidomimetic drug), a Gly-Sar-Sar tripeptide, a Gly-Sar-Sar-Sar tetrapeptide, and a Gly-Sar-Sar-Sar-Sar pentapeptide were administered at doses of 10 mg/kg each to 8- and 40-week-old SHRs. The peptides were all detected in their intact forms in the blood. There was a significantly promoted absorption of di/tripeptides in aged SHRs compared with young SHRs. In contrast, the absorption of tetra/pentapeptides was not affected by aging. PepT1 expression in the mid-jejunum was significantly increased in 40-week-old SHRs compared with 8-week-old SHRs, whereas aging did not alter the expression of claudin-1, a tight junction related protein. Thus, the present results suggest that SHR aging may enhance the absorption of di/tripeptides through the enhanced PepT1 transport route, although oli...

Effect of Aging on the Absorption of Small Peptides in Spontaneously Hypertensive Rats.

Recently,
in our experiments, we used the short-circuit
current technique to study the kinetic constants for nutrient
transporters in rat gastric-intestinal tract and the thickness of the intestinal
unstirred layer near the mucosa surface. It was shown that, during the process of aging, the number of nutrient monomer transporters in the small intestine
increases twofold, whereas the affinity of transporters to the correspondent
nutrients remains unchanged. The situation for peptides may be opposite. The
layer thickness in the vicinity of the mucosa surface, measured through
glucose, decreased during the process of aging. It was suggested that, in old
rats, the role of the digestive volume is more important, which results in an increase of the number of nutrient monomer transporters.

/pdf/rat-small-intestine-absorption-and-membrane-digestion-in-the-52e6pefb3s.pdf

Rat small intestine absorption and membrane digestion in the process of aging

Conditions in rat and turtle small intestine tissue where glucose and glycine transport is inhibited while glucose-induced Na+ transport is preserved are described. The generally accepted model for the Na+-dependent transporter (а single channel for the Na+ and nutrient) does not account for the data obtained from the analysis of the interaction between the transport of glucose, glycine, and Na+ at different temperatures and the effect of inhibitors оn these рroсеssеs. The phenomenon of temperature uncoupling of Na+ and nutrient transport саn best bе described bу а two-pathway model with а gate mechanism. According to this model, the Na+-dependent transporter has at least two pathways: оnе for Na+ and another for nutrients. The model рrovidеs for the passage of Na+ in both directions along а channel opened bу glucose. Experiments are carried out using the addition of glucose and glycine on backgrounds of glycine and glucose, respectively. It has been hypothesized that when all three transporters (for Na+, glucose and glycine) are unite in a single structure, then there should be “competitive relations” between short-circuit current changes on glycine and glucose for sodium ions passing through its transporter.

/pdf/the-physiological-model-of-na-dependent-transporters-for-jq92l53je4.pdf

Sergey T. Metelsky

Papers

Rat small intestine absorption and membrane digestion in the process of aging

The Physiological Model of Na + -Dependent Transporters for Glucose and Amino Acids in Rat and Turtle