Noise of secretagogue-induced inward currents dependent on extracellular calcium in rat mast cells.
We analyzed the noise of the inward currents induced by stimulation of rat peritoneal mast cells with compound 48/80 (48/80), a secretagogue, and examined the role of extracellular Ca2+ in generation of the large noise. In the presence of 2 mM Ca2+ in the external solution, the power density spectra of the 48/80-induced inward currents in most cells were fitted with the sum of two Lorentzian functions. The cut-off frequencies (fc) at -50 mV for the low and high frequency components were 16.3 +/- 7.3 (n = 10) and 180 +/- 95 (n = 9) Hz. Involvement of a cation-selective channel in the large noise was identified in some cells, but the single channel current amplitude estimated from parameters of the noise varied among cells (0.20-2.47 pA at -50 mV), thereby indicating that the currents were mediated by more than two classes of channel. The low frequency component of the 48/80-induced currents was suppressed by lowering the extracellular Ca2+ concentration to 1 microM with the addition of EGTA, without appreciable changes in the high frequency component. When the extracellular Ca2+ was reduced to 1 microM by EGTA 1 min prior to stimulation, 48/80 induced little or no currents in most cells and small currents in some cells. The power density spectra of the small currents were fitted mainly by a single Lorentzian curve with an fc of 150 +/- 5.8 Hz (n = 3). Re-admission of 1.3 mM Ca2+ produced a low frequency part of current noise with an fc of 18.8 (n = 2) Hz.(ABSTRACT TRUNCATED AT 250 WORDS)
Kuno
M
M
Department of Physiology, Osaka City University Medical School, Japan.
Kimura
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D004533:Egtazic Acid; D004553:Electric Conductivity / Q000187:drug effects; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D015220:Calcium Channels; D003189:p-Methoxy-N-methylphenethylamine; D004533:Egtazic Acid; D012964:Sodium; D002118:Calcium