Abstract
In this study using everted sacs of rat jejunum, we investigated the difference in absorption of two types of soybean peptides (small peptide: SP, and large peptide: LP). We investigated the influence of peptide length on absorption and intact transport of hydrolyzed soybean peptides. The everted sacs were incubated for 5 or 10min in bicarbonate-saline buffer containing a 1% (w/v) concentration of each soybean peptide. After the incubation, the amounts of free amino acids and peptides that were transported to the serosal fluids and the mucosa were measured with an automatic amino acid analyzer both before and after the hydrolysis of the serosal fluids and mucosa. The results indicated that SP was absorbed more rapidly than LP and that the more rapid absorption of SP was due to the greater intact transport of SP. When the everted sacs were made from jejunum that had been injured by intraperitoneal injection of cyclophosphamide (300mg/kg), no significant differences were noted between the absorption of SP and that of LP. We also ascertained that an aminopeptidase inhibitor (bestatin) decreased the aminopeptidase activities of the rat jejunum. In the presence of 1×10-4M bestatin in the incubation buffer, no significant differences were noted between the absorption of SP and that of LP. We conclude that SP is absorbed more rapidly than LP in normal rat jejunum due to greater intact transport.
