PT pretreatment inhibits 48/80-induced activation of Ca(+)-permeable channels in rat peritoneal mast cells.
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.
Kuno
M
M
Department of Physiology, Osaka City University Medical School, Japan.
Kawaguchi
J
J
Mukai
M
M
Nakamura
F
F
D000818:Animals; D001464:Barium / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability; D004553:Electric Conductivity; D016257:Fura-2; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D037342:Pertussis Toxin; D051381:Rats; D011919:Rats, Inbred Strains; D013050:Spectrometry, Fluorescence; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology*
D015220:Calcium Channels; D010566:Virulence Factors, Bordetella; D001464:Barium; D003189:p-Methoxy-N-methylphenethylamine; D037342:Pertussis Toxin; D016257:Fura-2