Basic Research
Copyright ©The Author(s) 2004. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jun 15, 2004; 10(12): 1763-1768
Published online Jun 15, 2004. doi: 10.3748/wjg.v10.i12.1763
Differential Cl- and HCO3- mediated anion secretion by different colonic cell types in response to tetromethylpyrazine
Jin-Xia Zhu, Ning Yang, Qiong He, Lai-Ling Tsang, Wen-Chao Zhao, Yiu-Wa Chung, Hsiao-Chang Chan
Jin-Xia Zhu, Lai-Ling Tsang, Yiu-Wa Chung, Hsiao-Chang Chan, Epithelial Cell Biology Research Center, Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong
Jin-Xia Zhu, Ning Yang, Qiong He, Wen-Chao Zhao, Department of Physiology, Medical School, Zhengzhou University, Zhengzhou, 450052, Henan Province, China
Author contributions: All authors contributed equally to the work.
Supported by the Innovation and Technology Commission of Hong Kong SAR, and Strategic program of The Chinese University of Hong Kong
Correspondence to: Professor Hsiao-Chang Chan, Epithelial Cell Biology Research Center, Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China. hsiaocchan@cuhk.edu.hk
Telephone: +852-26096839 Fax: +852-26035022
Received: October 20, 2003
Revised: January 24, 2004
Accepted: January 31, 2004
Published online: June 15, 2004
Abstract

AIM: Colonic epithelium is known to secrete both Cl- and HCO3-, but the secretory mechanisms of different colonic cell types are not fully understood. The present study aimed to investigate the differential activation of Cl- and HCO3-secretion by tetramethylpyrazine (TMP) in human crypt-like cell line, T84, and villus-like cell line, Caco-2, in comparison to the TMP-induced secretory response in freshly isolated rat colonic mucosa.

METHODS: Colonic epithelial anion secretion was studied by using the short circuit current (ISC) technique. RT-PCR was used to examine the expression of Na+-HCO3-- cotranspoter in different epithelial cell types.

RESULTS: TMP produced a concentration-dependent ISC which was increase in both T84 and Caco-2 cells. When extracellular Cl- was removed, TMP-induced ISC was abolished by 76.6% in T84 cells, but not in Caco-2 cells. However, after both Cl- and HCO3- were removed, TMP-induced ISC in Caco-2 cells was reduced to 10%. Bumetanide, an inhibitor of Na+-K+-Cl--cotranspoter, inhibited the TMP-induced ISC by 96.7% in T84 cells, but only 47.9% in Caco-2 cells. In the presence of bumetanide and 4, 4’-diisothiocyanostilbene-2, 2’-disulfonic acid, an inhibitor of Na+-HCO3- cotransporter, inhibited the TMP-induced current in Caco-2 cells by 93.3%. In freshly isolated rat colonic mucosa, TMP stimulated distinct ISC responses similar to that observed in T84 and Caco-2 cells depending on the concentration used. RT-PCR revealed that the expression of Na+-HCO3- cotransporter in Caco-2 cells was 4-fold more greater than that in T84 cells.

CONCLUSION: TMP exerts concentration-dependent differential effects on different colonic cell types with stimulation of predominant Cl- secretion by crypt cells at a lower concentration, but predominant HCO3- secretion by villus cells at a higher concentration, suggesting different roles of these cells in colonic Cl- and HCO3- secretion.

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