Contribution of surface epithelial cells to total conductance of
necturus gastric fundus mucosa.
Kottra, G., C. Iacovelli, R. Caroppo, S. Curci, P. Bakos, and E.
Fr[diaeresis]omter.
Zentrum der Physiologie, Klinikum der J. W. Goethe
-Universit[umlaut]at, Theodor Stern-Kai 7, 60590 Frankfurt am Main,
Germany, Istituto di Fisiologia Generale, Universit[grave]a degli
studi, Via Amendola 165 b, 70126, Bari, Italia
APStracts 2:0241G, 1995.
Microelectrode techniques were used to quantify the contribution of
surface epithelial cells (SEC) to transepithelial conductance (gt) of
Necturus gastric fundus mucosa. Transepithelial voltage (Vt) and
resistance (Rt) as well as the cell membrane potential (Vb) and
voltage divider ratio of SEC were measured. Freshly mounted
preparations did not respond to luminal amiloride (10 [mu]mol/l), but
within 2 to 3 h significant response developed (DVt = 3.8+/-1.2 mV,
DRt = 63+/-23 [omega]cm and DVb = -6.9+/-1.3 mV), indicating
activation of an apical Na+ conductance in SEC. Using circuit
analysis equations we calculate that SEC contribute 10.4 % to gt
under control conditions and 13.0 % after Na+ conductance activation.
Histamine (0.1 mmol/l), which stimulates the oxyntopeptic cells (OC),
increased Vt and decreased Rt, but did not significantly alter the
membrane resistances of SEC. As a result the contribution of SEC to
gt fell to 7.4 % or respectively 9.3 %. The data confirm that SEC are
poorly permeable, and that the major conductance path across gastric
mucosa leads through OC in the glands. The reason for the protracted
in-vitro activation of the apical Na+ conductance in SEC is not
known.
Received 9 May 1995; accepted in final form 8 November 1995.
APS Manuscript Number G195-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95