Potentiation of regulatory volume decrease by p2u purinoceptors in
hsg-pa cells.
Kim, Hyun Dju, Jesse W. Bowen, Marilyn R. James-Kracke, Linda A.
Landon, Jean M. Camden, Jane E. Burnett, and John T. Turner.
Department of Pharmacology, School of Medicine, University of
Missouri, Columbia, MO 65212 USA, phone: (314) 882-7186, FAX: (314)
884-4558
APStracts 2:0238C, 1995.
HSG-PA human salivary gland duct cells exhibit progressively increased
regulatory volume decrease (RVD) in response to decreased medium
osmolarity. The P2U purinoceptor agonist UTP causes a potentiation of
RVD, the extent of which is most pronounced in 220 mOsm medium and is
least apparent in 180 mOsm medium. We examined the underlying
mechanisms for this effect. Exposure of HSG-PA cells to UTP promotes
Ca2- mobilization, hyperpolarization and net K efflux, suggesting the
participation of Ca2--activated K channels in RVD. To delineate the
anion counterpart of K movement during RVD, cell swelling in the
presence of gramicidin, which abolishes the membrane potential, was
measured. In response to a sudden dilution in hypotonic media,
gramicidin-treated cells swelled immediately, followed by a
"secondary swelling" in 180 mOsm but not in 220 mOsm medium.
The results suggest that in 180 mOsm cells perform spontaneous RVD
mediated by increased anion conductance. In 220 mOsm medium where RVD
is minimal, the increase in anion conductance is marginal. In our
model of RVD in which cells were challenged by UTP, the ensuing
hyperpolarization provides the driving force for net Cl efflux, which
is confirmed by tracer flux studies during purinoceptor-activated
RVD. Thus, RVD, which has long been regarded as a self-sufficient
cellular program, appears to be subject to extracellular control in
HSG-PA cells through receptor-mediated processes.
Received 23 March 1995; accepted in final form 22 June 1995.
APS Manuscript Number C164-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.