Figure 5. Protein kinase A (PKA) is crucial for butyrate-induced increase of hPepT1 promoter activity in Caco2-BBE cells.

A) Caco2-BBE cells transfected with the full-length hPepT1 promoter construct were pre-treated for 1 h with 40 or 100 µM H89, a specific PKA inhibitor, and stimulated with 5 mM butyrate for 24 h. Luciferase activity relative to hPepT1 promoter activity was measured. Data were normalized by Renilla activity and expressed as fold increases compared with control cells. B) Caco2-BBE cells pre-treated or untreated with 100 µM H89 for 1 h were stimulated with 5 mM butyrate for 24 h. hPepT1-mediated [¹⁴C]Glycine-Sarcosine specific uptake was assessed as described in the Materials and Methods. Values represent means±S.E. of three determinations. *P<0.05; **P<0.005; ***P<0.001.