Affiliation:
1. Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Queensland, Brisbane, Australia; and Universitäts-Kinderklinik, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
Abstract
The colonic epithelium has both absorptive and secretory functions. The transport is characterized by a net absorption of NaCl, short-chain fatty acids (SCFA), and water, allowing extrusion of a feces with very little water and salt content. In addition, the epithelium does secret mucus, bicarbonate, and KCl. Polarized distribution of transport proteins in both luminal and basolateral membranes enables efficient salt transport in both directions, probably even within an individual cell. Meanwhile, most of the participating transport proteins have been identified, and their function has been studied in detail. Absorption of NaCl is a rather steady process that is controlled by steroid hormones regulating the expression of epithelial Na+channels (ENaC), the Na+-K+-ATPase, and additional modulating factors such as the serum- and glucocorticoid-regulated kinase SGK. Acute regulation of absorption may occur by a Na+feedback mechanism and the cystic fibrosis transmembrane conductance regulator (CFTR). Cl−secretion in the adult colon relies on luminal CFTR, which is a cAMP-regulated Cl−channel and a regulator of other transport proteins. As a consequence, mutations in CFTR result in both impaired Cl−secretion and enhanced Na+absorption in the colon of cystic fibrosis (CF) patients. Ca2+- and cAMP-activated basolateral K+channels support both secretion and absorption of electrolytes and work in concert with additional regulatory proteins, which determine their functional and pharmacological profile. Knowledge of the mechanisms of electrolyte transport in the colon enables the development of new strategies for the treatment of CF and secretory diarrhea. It will also lead to a better understanding of the pathophysiological events during inflammatory bowel disease and development of colonic carcinoma.
Publisher
American Physiological Society
Subject
Physiology (medical),Molecular Biology,Physiology,General Medicine
Cited by
558 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献