Effects of protein kinase inhibitors on the serotonin-mediated repression of the NHE3 core promoter activity. Differentiated C2BBe1 cells were transiently transfected with the p-95/+5. After serum-starvation, cell were treated without (control) or with the chelerythrine chloride (CC) (A), GÖ6976 (B), or Rp-8-Br-cAMP (C), for 1 h prior to further incubation in the presence or absence of 5-HT for 16 h. The luciferase activities are presented as percentage of the control (n=3, mean ± S.E.). ‡, *** P < 0.0005; * P = 0.49.