Perimetric [Ca2+]i rise and exocytosis detected by ultraviolet laser scanning confocal microscopy in rat peritoneal mast cells.
It has been reported that in dialysed mast cells an increase in mean [Ca2+]i is neither necessary nor sufficient for secretion; however, it is possible that juxtamembranal [Ca2+]i may exceed the mean [Ca2+]i before exocytosis. The present study was carried out to analyse spatial and temporal dynamics of [Ca2+]i and concomitant exocytosis in intact rat peritoneal mast cells using UV laser scanning confocal microscopy. Stimulation with Compound 48/80 (16 microM) increased mean [Ca2+]i, causing an initial rapid elevation from 40 to 200 nM, which lasted for 6 s and was followed by a delayed secondary increase to 600 nM. Exocytotic images were seen in the cell perimeter 16 s after the stimulation. Perimetric and nuclear [Ca2+]i increased to several mumoles per litre, while that in the intermediate region remained low. In a Ca(2+)-deficient environment, Compound 48/80 still increased perimetric [Ca2+]i to micromolar values and induced exocytosis. This study clearly indicates, for the first time, that a perimetric increase in [Ca2+]i to micromolar levels precedes exocytosis, in intact, as opposed to permeabilized cells.
Habara
Y
Y
Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
Kanno
T
T
D000818:Animals; D002118:Calcium / Q000502:physiology*; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D005089:Exocytosis / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D008407:Mast Cells / Q000502:physiology*; D018613:Microscopy, Confocal; D008860:Microscopy, Ultraviolet / Q000379:methods*; D010537:Peritoneum / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D003189:p-Methoxy-N-methylphenethylamine; D019204:GTP-Binding Proteins; D002118:Calcium