Regulating effect of TongXie-YaoFang on colonic epithelial secretion via Cl(-) and HCO(3)(-) channel

AIM: To investigate the pharmacological effect of TongXie-YaoFang (TXYF) formula, a Chinese herbal formula, on Diarrhea-predominant irritable bowel syndrome (D-IBS) rats. METHODS: In a neonatal maternal separation plus restraint stress (NMS + RS) model of D-IBS, male Sprague Dawley rats were randomly divided into two groups (NMS + RS group and TXYF-formula group) with no handlings were used as controls (NH group). Starting from postnatal day 60, rats in TXYF-formula group were administered TXYF-formula (4.92 g/100 g bodyweight) orally twice a day for 14 consecutive days while NH group and NMS + RS group were given distilled water. Using short-circuit current technology, we observed 5-HT-induced changes of current across ion channels, such as cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, epithelial Na(+) channel (ENaC), Ca(2+)-dependent Cl(-) channel (CACC), Na(+)-K(+)-2Cl(-) co-transporter (NKCC), and Na(+)-HCO(3)(-) co-transporter (NBC), in the colonic epithelium of three groups after exposure to drugs and specific blockers with a Power Lab System (AD Instruments International). RESULTS: Under basal conditions, the changes of short-circuit current (∆Isc, µA/cm(2)) induced by 5-HT were similar in NH group and TXYF-formula group, and both higher than NMS + RS group (70.86 µA/cm(2 )± 12.32 µA/cm(2), 67.67 µA/cm(2 )± 11.68 µA/cm(2 )vs 38.8 µA/cm(2 )± 7.25 µA/cm(2), P < 0.01, respectively). When CACC was blocked by 4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid, 5-HT-induced ∆Isc was smaller in NMS + RS group than in NH group and TXYF-formula group, respectively (48.41 µA/cm(2 )± 13.15 µA/cm(2 )vs 74.62 µA/cm(2 )± 10.73 µA/cm(2), 69.22 µA/cm(2 )± 11.7 µA/cm(2), P < 0.05, respectively). The similar result could be obtained when ENaC was blocked by Amiloride (44.69 µA/cm(2 )± 12.58 µA/cm(2 )vs 62.05 µA/cm(2 )± 11.26 µA/cm(2), 62.11 µA/cm(2 )± 12.01 µA/cm(2), P < 0.05, respectively). However, when CFTR Cl(-) channel was blocked by 1,1-dimethyl piperidinium chloride (DPC), 5-HT-induced ∆Isc did not significantly differ in three groups (42.28 µA/cm(2 )± 10.61 µA/cm(2 )vs 51.48 µA/cm(2 )± 6.56 µA/cm(2 )vs 47.75 µA/cm(2 )± 7.99 µA/cm(2), P > 0.05, respectively). The similar results could also be obtained in three groups when NBC and NKCC were respectively blocked by their blockers. CONCLUSION: TXYF-formula can regulate the Cl(-) and HCO(3)(-) secretion of colonic mucosa via CFTR Cl(-) channel, Cl(-)/HCO(3)(-) exchanger, NBC and NKCC co-transporters.