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Título
Calcium dynamics in catecholamine-containing secretory vesicles
Autor
Año del Documento
2005
Editorial
Elsevier Ltd.
Descripción
Producción Científica
Documento Fuente
Cell Calcium, 2005, vol. 37, p. 555-564
Résumé
We have used an aequorin chimera targeted to the membrane of the secretory granules to monitor the free [Ca2+] inside them in neurosecretory
PC12 cells. More than 95% of the probe was located in a compartment with an homogeneous [Ca2+] around 40 M. Cell stimulation with
either ATP, caffeine or high-K+ depolarization increased cytosolic [Ca2+] and decreased secretory granule [Ca2+] ([Ca2+]SG). Inositol-(1,4,5)-
trisphosphate, cyclic ADP ribose and nicotinic acid adenine dinucleotide phosphate were all ineffective to release Ca2+ from the granules.
Changes in cytosolic [Na+] (0–140 mM) or [Ca2+] (0–10 M) did not modify either ([Ca2+]SG). Instead, [Ca2+]SG was highly sensitive to
changes in the pH gradient between the cytosol and the granules. Both carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) and
nigericin, as well as cytosolic acidification, reversibly decreased [Ca2+]SG, while cytosolic alcalinization reversibly increased [Ca2+]SG. These
results are consistent with the operation of a H+/Ca2+ antiporter in the vesicular membrane. This antiporter could also mediate the effects
of ATP, caffeine and high-K+ on [Ca2+]SG, because all of them induced a transient cytosolic acidification. The FCCP-induced decrease in
[Ca2+]SG was reversible in 10–15 min even in the absence of cytosolic Ca2+ or ATP, suggesting that most of the calcium content of the vesicles
is bound to a slowly exchanging Ca2+ buffer. This large store buffers [Ca2+]SG changes in the long-term but allows highly dynamic free [Ca2+]SG
changes to occur in seconds or minutes.
Materias (normalizadas)
Calcio en el organismo
ISSN
0143-4160
Revisión por pares
SI
Idioma
eng
Derechos
openAccess
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