IMPEDANCE ANALYSIS FOR THE DETERMINATION OF EPITHELIAL AND SUBEPITHELIAL RESISTANCE IN INTESTINAL TISSUES

The barrier function of the intestinal wall plays a key role in body h omeostasis and defense against noxious agents. Conventional Ussing cha mber techniques determine the overall transmural resistance but do not differentiate epithelial and subepithelial tissues. The barrier funct ion, however, resides in the epithelial cell layer only. Transmural. i mpedance analysis can solve this problem, if adequate models are appli ed. We show that: (i) epithelial and subepithelial impedances are addi tive, (ii) the epithelium proper can be represented by a very general electrical model, which demonstrates short-circuiting at high frequenc ies (due to cell membrane capacitances), and (iii) the reactance of su bepithelial tissue can be described phenomenologically. Using an empir ical expression for description of the subepithelial impedance, the pr esent method allows the determination of the epithelial and the subepi thelial resistance. This was exemplified in rat ileum, which defied ad equate impedance analysis so far. Of the transmural DC resistance of 6 1 +/- 5 Omega.cm(2) (n = 8) the subepithelial contribution was 28 +/- 2 Omega.cm(2) and the epithelial resistance was 33 +/- 4 Omega.cm(2). (C) 1998 Elsevier Science B.V. All rights reserved.