期刊
CHANNELS
卷 3, 期 2, 页码 101-109出版社
TAYLOR & FRANCIS INC
DOI: 10.4161/chan.3.2.7866
关键词
beta-cell exocytosis; phasic exocytosis; tonic exocytosis; immediately releasable pool; highly calcium sensitive pool
资金
- National Institutes of Health [4RO1-DK37380, ROI-DK20579]
- National Institutes of Health Medical Scientist Training Grant [5T32 GM07281]
In response to depolarizations that open voltage dependent Ca2+ channels single porcine beta-cells display heterogeneous time courses of exocytosis. Some cells display phasic exocytosis that is triggered by individual or short burst of action potentials typically characteristic of glucose-induced electrical activity or brief voltage clamp depolarization. Other cells, singularly or additionally, display tonic exocytosis that (i) is triggered during prolonged ( up to seconds-long) depolarizations to voltages (-30 to -20 mV), and (ii) coincides with rises in global cytosolic [Ca2+] >500 nM. We suggest that tonic exocytosis (i) likely results from a recently described pool of granules that is more Ca2+ sensitive and less co-localized with voltage-sensitive Ca2+ entry channels than that contributing to phasic exocytosis and (ii) helps tune exocytosis to glucose-induced electrical activity when the latter consists of spike activity followed by intervals of plateau depolarization to nearly -20 mV.
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