AJP - Cell Physiology, Vol 256, Issue 3 C560-C568, Copyright © 1989 by American Physiological Society
A patch-clamp study: secretagogue-induced currents in rat peritoneal mast cells
M. Kuno, T. Okada and T. Shibata
Department of Physiology, Osaka City University Medical School, Japan.
Ca2+ entry through plasma membrane has been considered to play a
significant role in elevating cytosolic free Ca2+ concentrations during
stimulus-secretion coupling in mast cells, but electrophysiological
evidence of the Ca2+ channels is lacking. We examined the properties of
secretagogue (compound 48/80)-induced currents in rat peritoneal mast
cells, using the patch-clamp technique. In the whole cell recordings, the
addition of compound 48/80 induced transient currents that were suppressed
by Cd or reduced by ethylene glycol-bis(beta-aminoethyl
ether)-N,N,N',N'-tetraacetic acid (EGTA). In Ringer solution containing 2
mM Ca2+, the current-voltage relation was fairly linear from -100 to 50 mV
and the reversal potential was 14 +/- 10.1 mV (n = 9). When the external
Ca2+ was approximately 1 microM, the compound 48/80-induced currents were
marginal, but readmission of Ca2+ or Ba2+ to the bath solution led to an
appearance of the currents. In the cell-attached patches, the stimulation
enhanced the activity of inward current mediated by Ba2+. The unitary
inward Ba2+ current was characterized by the unitary conductance of 10.5
+/- 2.0 pS (n = 10) with isotonic BaCl2 pipette solution, the extrapolated
reversal potential of 60.7 +/- 16.0 mV (n = 10) positive to the resting
membrane potentials. The percent open time of the inward Ba2+ current
channel was not appreciably changed by voltage. In some whole cell
recordings, an increase in openings of the cation-selective channel (20-45
pS) was identified in the stimulated cells. When the external Na+ was
completely replaced by choline+, the compound 48/80-induced currents had a
fairly linear current-voltage relation.(ABSTRACT TRUNCATED AT 250 WORDS)
