Abstract
We attempted to develop an evaluation model for protein digestion and absorption using the rat portal vein catheter placement
method. Sodium caseinate solution was continuously administered from a gastric catheter in rats into which catheters were placed
in the stomach and portal vein, and the digestive absorption of protein was measured based on the time course of changes in amino
acid concentrations in the portal vein as an index. When 5% sodium caseinate solution was continuously administered (11.25 mL/
kg/h) from the gastric catheter using a peristaltic pump, the portal blood concentrations of eight amino acids (glutamine, tyrosine,
methionine, tryptophan, valine, phenylalanine, isoleucine and leucine) increased with time. Significant increases were observed
for these eight amino acids when compared with pre-administration values (0 minutes) up to 180 minutes after administration.
Therefore, the state of protein digestion and absorption can be observed using portal blood amino acid concentrations as indicators.
Green tea is reported to suppress protein absorption, and it was therefore investigated whether this inhibitory action could
be confirmed using this experimental model. A single administration of a 20% green tea extract (7.2 mL/kg) and continuously
administered 5% sodium caseinate solution to rats resulted in a significant inhibitory effect in the portal blood concentrations of
these eight amino acids.
These results confirm that the rat portal vein catheter placement method is useful as an experimental model for evaluating the
digestion and absorption of proteins.
