Effect of TongXie-YaoFang on Cl− and HCO3- Transport in Diarrhea-Predominant Irritable Bowel Syndrome Rats.

TongXie-YaoFang (TXYF) can effectively alleviate the symptoms of diarrhea-predominant irritable bowel syndrome (D-IBS) patients. However, the curative mechanism has not been fully clarified. The study was designed to investigate the effect of TXYF on the colonic ion transport induced by serotonin (5-HT) in D-IBS rats. A method of multiple stress (neonatal maternal separation (NMS) combined with restraint stress (RS)) was used to induce the D-IBS model. The model rats were randomly divided into two groups: NMS + RS group and TXYF-formula group, and the normal control (no handling) rats were classified as NH group. In the NMS + RS group, the change of short-circuit current (ΔIsc) induced by 5-HT was lower than that in the NH and TXYF-formula groups. After removing of the extracellular Cl⁻ or HCO₃- or basolateral Na⁺ or blocking the cystic fibrosis transmembrane conductance regulator (CFTR), Na⁺-K⁺-2Cl⁻ cotransporter (NKCC), Na+-HCO₃- cotransporter, Cl-/HCO₃- exchanger, K⁺ channel, or Na⁺/K⁺-ATPase, respectively, there was no difference in 5-HT-induced ΔIsc among the three groups. These data suggest that TXYF can regulate 5-HT-induced Cl⁻ and HCO₃- secretion, possibly mediated by the combined action of CFTR, NKCC, Na⁺-HCO₃- cotransporter, Cl-/HCO₃- exchanger, K⁺ channel, and Na⁺/K⁺-ATPase. [ABSTRACT FROM AUTHOR]