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

Abstract

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 (ΔI sc) 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 ΔI sc 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.

Figure 1

Comparison of basal electrophysiological properties and 5-HT-induced ΔI _sc of colonic mucosa among the three groups (means ± SEM, n = 18). Basal I _sc (a); basal potential difference (PD) (b); basal transmembrane resistance (TR) (c); ΔI _sc induced by 5-HT (d). ^∗ P < 0.01 versus NH group; ^▲ P < 0.01 versus NMS + RS group.

Figure 2

Comparison of 5-HT-induced ΔI _sc of colonic mucosa in Cl⁻-free, HCO₃ ⁻-free, or Cl⁻- and HCO₃ ⁻-free (a); apical Na⁺-free (b); basolateral Na⁺-free (c) K-HS among the three groups (means ± SEM, n = 6). ^∗ P < 0.01 versus NH group; ^▲ P < 0.05 versus NMS + RS group.

Figure 3

Comparison of 5-HT-induced ΔI _sc of colonic mucosa after apical application of DPC, a nonselective Cl⁻ channel blocker; glibenclamide or CFTR(inh)-172, the cAMP-independent Cl⁻ channel blockers; and DIDS, a Ca²⁺-independent Cl⁻ channel blocker (a); apical application of amiloride, an epithelial Na⁺ channel blocker (b); basolateral application of BaCl₂, a K⁺ channel inhibitor (c) among the three groups (means ± SEM, n = 6). ^∗ P < 0.05 and ^∗∗ P < 0.01 versus NH group; ^▲ P < 0.05 and ^▲▲ P < 0.01 versus NMS + RS group.

Figure 4

Comparison of 5-HT-induced ΔI _sc of colonic mucosa in the basolateral presence of Na⁺-K⁺-2Cl⁻ cotransporter (NKCC) inhibitor, bumetanide; Na⁺-HCO₃ ⁻ cotransporter or Cl⁻/HCO₃ ⁻ exchanger inhibitor, SITS; Na⁺/K⁺-ATPase inhibitor, ouabain, among the three groups (means ± SEM, n = 6).