Volume-regulatory taurine release in human tracheal 9hteo- and
multidrug resistant 9hteo-/dx cells.
Galietta, Luis J. V., Giovanni Romeo, and Olga Zegarra-Moran.
Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini,
Genova-16148, Italy
APStracts 3:0094C, 1996.
The intracellular taurine release evoked by hypotonic shock is
accomplished by volume-activated Cl- channels whose activity has been
related to the expression of the multidrug resistance protein (MDR
-1). We studied taurine transport in 9HTEo- cells and in the derived
cell line 9HTEo-/Dx expressing MDR-1. 3H-taurine release from
preloaded cells increased upon reduction of extracellular osmolality.
This process was not inhibited by preincubation with phorbol 12
-myristate 13-acetate, but was reduced by inhibitors of volume
-sensitive Cl- channel such as 1,9-dideoxiforskolin, La3+ and
arachidonate. Verapamil, a substrate of MDR-1, increased the
osmotically-evoked taurine efflux. Replacement of extracellular Cl-
with I- or gluconate, or of extracellular Na+ with Li+ significantly
reduced the taurine efflux whereas substitution of NMDG+ for Na+
increased it. Application of ATP and 2-chloroadenosine stimulated the
efflux in isotonic medium. No differences were seen between 9HTEo-
and 9HTEo-/Dx cells with respect to hypotonically-induced taurine
efflux and the response to phorbol ester, channel blockers, ion
replacement and purinergic agents. Our results reveal novel
properties of the osmotically-induced taurine release and demonstrate
its independence from MDR-1 gene expression.
Received 27 December 1995; accepted in final form 12 March 1996.
APS Manuscript Number C765-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96