A patch-clamp study: secretagogue-induced currents in rat peritoneal mast cells.
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)
Kuno
M
M
Department of Physiology, Osaka City University Medical School, Japan.
Okada
T
T
Shibata
T
T
D000818:Animals; D001464:Barium / Q000494:pharmacology; D017609:Barium Compounds; D002104:Cadmium / Q000494:pharmacology; D019256:Cadmium Chloride; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D002712:Chlorides; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D066298:In Vitro Techniques; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D017609:Barium Compounds; D015220:Calcium Channels; D002712:Chlorides; D002104:Cadmium; C024986:barium chloride; D002586:Cesium; D001464:Barium; D003189:p-Methoxy-N-methylphenethylamine; D004533:Egtazic Acid; C028019:cesium chloride; D019256:Cadmium Chloride; D002122:Calcium Chloride