R. Fernandezchacon et Ga. Detoledo, CYTOSOLIC CALCIUM FACILITATES RELEASE OF SECRETORY PRODUCTS AFTER EXOCYTOTIC VESICLE FUSION, FEBS letters, 363(3), 1995, pp. 221-225
We monitored single vesicle exocytosis by simultaneous measurements of
cell membrane capacitance as an indicator of fusion and amperometric
detection of serotonin release, We show here that vesicle-plasma membr
ane fusion in rat mast cell grannies is followed by a variable, expone
ntially distributed, delay before bulk release, This delay reflects th
e time required for the expansion of the exocytotic fusion pore, lasti
ng, on average, 231 ms in resting cytosolic calcium, [Ca2+](i) (50 nM)
, In the presence of [Ca2+](i) in the low micromollar range, the lag b
etween fusion and release was reduced to 123 ms. The characteristics o
f the amperometric signals were unchanged by [Ca2+](i). These results
show a novel site of regulation in the exocytotic process, the fusion
pore, which may represent a different mechanism facilitating transmitt
er release.