Cellular hypercalcemia is an early event in deoxycholate injury of
rabbit gastric mucosal cells.
Dziki, Adam J., Shmuel Batzri, John W. Harmon, Mark Molloy.
Departments of Surgery, VA Medical Center, Washington, DC, and
Uniformed Services University of the Health Sciences, Bethesda,
MD.
APStracts 2:0082G, 1995.
Calcium entry into the cell may be an early event in the
pathophysiology of bile salt-induced gastric mucosal injury. The aim
of this study was to characterize the rise in cytosolic free calcium
associated with bile salt injury and its association with cell injury
and death. Rabbit gastric mucosal cells were preloaded with the Ca2+
indicator FURA-2 AM for 20 min at 37oC, and then exposed to graded
concentrations of the bile salt deoxycholate (DC). Cytosolic free
calcium concentration ([Ca2+]i) was estimated by spectrofluorometry.
The resting [Ca2+]i in gastric cells was 177 +/- 15 nM (n=6). When
the cells were subjected to 0.5 mM DC, there was a time dependent
rise in [Ca2+]i. An increase in [Ca2+]i was observed within 2 min at
which time [Ca2+]i rose from 177 +/- 15 nM to 480 +/- 30 nM. The
maximal increase in [Ca2+]i was observed after 20 min of exposure to
0.5 mM DC (639 +/- 49 nM), and [Ca2+]i remained unchanged for at
least 2 hr. The increase in [Ca2+]i depended on the concentration of
DC. The minimum effective dose of DC was 0.2 mM with which [Ca2+]i
was increased by 1.6-fold (from 177 to 285 nM). At 0.5 mM DC also
caused a rise in 45Ca2+ influx into the cells and reduced the
viability of gastric cells from 96% to 58% at 2 h. The DC-induced
rise in cytosolic free calcium depended on the presence of
extracellular calcium. In the absence of extracellular Ca2+ there was
no rise in cytosolic calcium and gastric cells were protected from
cell death caused by DC. The DC-induced cell death was reduced from
26% to 10% and from 37% to 16% at 60 and 90 min, respectively, by
removal of extracellular calcium. The association of DC with gastric
cells was not altered by removing extracellular calcium. This
suggests decreased DC-induced injury in the absence of extracellular
calcium is due to the protection from cellular hypercalcemia rather
than some other mechanism related to reduced binding/association of
DC to gastric cells.. These experiments show that rising [Ca2+]i
appears to be an early pathophysiological event in bile salt-induced
cellular injury, and that extracellular calcium is critical to
produce this effect.
Received 11 August 1993; accepted in final form 21 February 195.
APS Manuscript Number G323-3.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.