In:
American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 292, No. 2 ( 2007-02), p. C896-C908
Abstract:
How the endoplasmic reticulum (ER) and mitochondria communicate with each other and how they regulate plasmalemmal Ca 2+ entry were studied in cultured rat brown adipocytes. Cytoplasmic Ca 2+ or Mg 2+ and mitochondrial membrane potential were measured by fluorometry. The sustained component of rises in cytoplasmic Ca 2+ concentration ([Ca 2+ ] i ) produced by thapsigargin was abolished by removing extracellular Ca 2+ , depressed by depleting extracellular Na + , and enhanced by raising extracellular pH. FCCP, dinitrophenol, and rotenone caused bi- or triphasic rises in [Ca 2+ ] i , in which the first phase was accompanied by mitochondrial depolarization. The FCCP-induced first phase was partially inhibited by oligomycin but not by ruthenium red, cyclosporine A, U-73122, a Ca 2+ -free EGTA solution, and an Na + -free solution. The FCCP-induced second phase paralleling mitochondrial repolarization was partially blocked by removing extracellular Ca 2+ and fully blocked by oligomycin but not by thapsigargin or an Na + -deficient solution, was accompanied by a rise in cytoplasmic Mg 2+ concentration, and was summated with a high pH-induced rise in [Ca 2+ ] i , whereas the extracellular Ca 2+ -independent component was blocked by U-73122 and cyclopiazonic acid. The FCCP-induced third phase was blocked by removing Ca 2+ but not by thapsigargin, depressed by decreasing Na + , and enhanced by raising pH. Cyclopiazonic acid-evoked rises in [Ca 2+ ] i in a Ca 2+ -free solution were depressed after FCCP actions. Thus mitochondrial uncoupling causes Ca 2+ release, activating Ca 2+ release from the ER and store-operated Ca 2+ entry, and directly elicits a novel plasmalemmal Ca 2+ entry, whereas Ca 2+ release from the ER activates Ca 2+ accumulation in, or release from, mitochondria, indicating bidirectional mitochondria-ER couplings in rat brown adipocytes.
Type of Medium:
Online Resource
ISSN:
0363-6143
,
1522-1563
DOI:
10.1152/ajpcell.00649.2005
Language:
English
Publisher:
American Physiological Society
Publication Date:
2007
detail.hit.zdb_id:
1477334-X
SSG:
12
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