AJP - Cell Physiology, Vol 259, Issue 5 C715-C722, Copyright © 1990 by American Physiological Society
PT pretreatment inhibits 48/80-induced activation of Ca(+)-permeable channels in rat peritoneal mast cells
M. Kuno, J. Kawaguchi, M. Mukai and F. Nakamura
Department of Physiology, Osaka City University Medical School, Japan.
We recently reported that the secretagogue, compound 48/80, activated
Ca2(+)-permeable channels of mast cells possibly via a second messenger
[Kuno, Okada, and Shibata. Am. J. Physiol. 256 (Cell Physiol. 25):
C560-C568, 1989]. The effects of pretreatment with pertussis toxin (PT) on
compound 48/80 (48/80)-induced activation of the Ca2(+)-permeable channel
have now been investigated by measuring Ca2+ signals of cell suspensions
using the Ca2+ indicator fura-2 and by recording Ba2+ currents through the
channel using the patch-clamp technique. In the presence of extracellular
Ca2+, the fluorescence change was biphasic, with an immediate rise and a
delayed peak at room temperature. The delayed peak, mainly due to Ca2+
entry through plasma membranes, was greatly reduced by pretreatment with
PT. The quenching of the fluorescence by 48/80-induced Mn2+ influx was also
decreased by PT, whereas the Ca2+ transients due to Ca2+ release from the
intracellular stores apparently did not change. In patch-clamp recordings
from cell-attached patches with pipettes containing isotonic Ba2+, the
48/80-induced Ba2+ currents were either suppressed or delayed in the
PT-treated cells, under conditions where degranulation was absent. These
results suggest that PT-sensitive GTP-binding protein is involved in
activating the Ca2(+)-permeable channel in mast cells during
stimulus-secretion coupling.
