AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 4 545-R548, Copyright © 1987 by American Physiological Society
Effect of diltiazem on intracellular Ca2+ mobilization in hepatocytes during endotoxic shock
S. R. Maitra and M. M. Sayeed
Department of Physiology, Loyola University Stritch School of Medicine, Maywood, Illinois 60153.
Effects of Salmonella enteritidis endotoxin on intracellular Ca2+
mobilization were studied in hepatocytes. Rats were given intravenous
injections of saline (control), endotoxin (20 mg/kg), or endotoxin (20
mg/kg) plus diltiazem (1.2 mg/kg). They were killed 5 h later, at which
time endotoxin-injected rats showed signs of shock. The involvement of
myoinositol 1,4,5-trisphosphate (IP3) and arachidonic acid (AA) in
intracellular Ca2+ mobilization was tested using saponin-permeabilized
hepatocytes. Added Ca2+ was sequestered by intracellular organelles in the
presence of ATP until the medium free Ca2+ concentration was lowered to a
near steady-state level. In control cells subsequent addition of 10(-6) M
IP3 and AA, respectively, caused a rapid increase in free Ca2+
concentration from 130 +/- 31 to 257 +/- 54 nM (P less than 0.01) and from
111 +/- 21 to 196 +/- 37 (P less than 0.01). By use of experimental
conditions designed to permit selective Ca2+ accumulation, it was
determined that all of the Ca2+ released by IP3 and AA originated from the
endoplasmic reticulum. The intracellular release of Ca2+ by IP3 and AA was
significantly attenuated in endotoxic shock. Treatment of endotoxic rats
with a calcium channel blocker, diltiazem, effected an increase in free
Ca2+ concentration by IP3 from 124 +/- 18 to 240 +/- 41 nM (P less than
0.01) and by AA from 109 +/- 15 to 192 +/- 32 (P less than 0.01). These
data suggest that during endotoxic shock there is an attenuation of IP3-
and AA-induced intracellular Ca2+ release, which could be prevented by
treatment of animals with diltiazem.
