Background and Aims: Many investigations suggested that peptide nutrition had a clinical advantage for nitrogen absorption. Recently, the cDNA encoding the H+/peptide cotransporter PepT1 was cloned. However, the regulatory mechanism of PepT1 expression under malnourished conditions has not been elucidated. The aim of this study was to clarify regulatory mechanisms of PepT1 expression. Methods: Sprague-Dawley rats were starved for 4 days, semistarved (50% amount of control) for 10 days, or given total parenteral nutrition (TPN) for 10 days. Rats with free feeding were used as control. Among those groups, the changes of PepT1 mRNA level in the jejunal mucosa and PepT1 protein density at the brush-border membranes were examined by Northern blot and by Western blot analysis, respectively. Results: Both starvation and TPN treatment caused a significant decrease in mucosal weight by 41 and 50% respectively. PepT1 mRNA level increased to 179% in the starved group and also to 161 and 164% in the TPN and semistarved groups, respectively. In contrast, sodium-dependent glucose transporter 1 mRNA expression showed no significant change. PepT1 protein density showed similar changes with the mRNA. Conclusions: PepT1 gene expression was significantly enhanced under the malnourished conditions in spite of atrophic changes of intestinal mucosa.

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