Time course of Ca2+ concentration triggering exocytosis in neuroendocrine cells.

AUTOR(ES)

Chow, R H

RESUMO

We have used the secretory response of chromaffin cells to estimate the submembrane intracellular Ca2+ concentration ([Ca2+]i) "seen" by secretory granules during short depolarizations. The rate of secretion during a depolarization was assessed by combining the electrochemical method of amperometry and electrical capacitance measurements. The rate was then related to [Ca2+]i based on a previous characterization of how Ca2+ affects the dynamics of vesicle priming and fusion in chromaffin cells [Heinemann, C., Chow, R. H., Neher, E. & Zucker, R. S. (1994) Biophys. J. 67, in press]. Calculated [Ca2+]i rose during the depolarization to a peak of < 10 microM, then decayed over tens of milliseconds. In synapses, vesicles are presumed to be located within nanometers of Ca2+ channels where [Ca2+]i is believed to rise in only microseconds to near steady-state levels of hundreds of micromolar. Channel closure should lead to a decrease in [Ca2+]i also in microseconds. Our findings of the slower time course and the lower peak [Ca2+]i suggest that in chromaffin cells, unlike synapses, Ca2+ channels and vesicles are not strictly colocalized. This idea is consistent with previously published data on dense-core vesicle secretion from diverse cell types.

Documentos Relacionados

• Ca2+ triggers massive exocytosis in Chinese hamster ovary cells.
• Critical intracellular Ca2+ concentration for all-or-none Ca2+ spiking in single smooth muscle cells.
• Monitoring dynamic changes in free Ca2+ concentration in the endoplasmic reticulum of intact cells.
• Ca2+ Channels in Higher Plant Cells.
• Muscarinic agonists and ATP increase the intracellular Ca2+ concentration in chick cochlear hair cells.