Osmosignaung and VoLume Regulation in Intestinal Epithelial Cens

Christina H. Lim, Alice G. M. Bot, Hugo R. de Jonge, and Ben C. Tilly

Contents

1. Introduction 326

2. Properties of Ion Channels and Transporters Activated During

RVD in Intestinal Epithelial Cells 326

3. Osmosensing and Signaling 328

4. Model Systems 330

5. Measuring Ionic Responses 331

5.1. Whole cell patch clamp 331

5.2. Isotope efflux assay 333

5.3. Ussing chamber experiments 335

5.4. Fluorometric quantification of intracellular ion concentrations 337

6. Concluding Remarks 338 References 338

Abstract

Most cells have to perform their physiological functions under a variable osmotic stress, which, because of the relatively high permeability of the plasma membrane for water, may result in frequent alterations in cell size. Intestinal epithelial cells are especially prone to changes in cell volume because of their high capacity of salt and water transport and the high membrane expression of various nutrient transporters. Therefore, to avoid excessive shrinkage or swelling, enter-ocytes, like most cell types, have developed efficient mechanisms to maintain osmotic balance. This chapter reviews selected model systems that can be used to investigate cell volume regulation in intestinal epithelial cells, with emphasis on the regulatory volume decrease, and the methods available to study the

Department of Biochemistry, Erasmus University Medical Center, Rotterdam, The Netherlands

Methods in Enzymology, Volume 428 © 2007 Elsevier Inc.

ISSN 0076-6879, DOI: 10.1016/S0076-6879(07)28019-X All rights reserved.

compensatory redistribution of (organic) osmolytes. In addition, a brief summary is presented of the pathways involved in osmosensing and osmosignaling in the intestine.

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