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Mode of mitochondrial Ca2+ clearance and its influence on secretory responses in stimulated chromaffin cells.
- Source :
- Cell Calcium; Jan2006, Vol. 39 Issue 1, p35-46, 12p
- Publication Year :
- 2006
-
Abstract
- Abstract: To study the role of mitochondrial Ca<superscript>2+</superscript> clearance in stimulated cells, changes in free Ca<superscript>2+</superscript> concentration in the cytosol, [Ca<superscript>2+</superscript>]<subscript>c</subscript> and that in mitochondria, [Ca<superscript>2+</superscript>]<subscript>m</subscript> along with secretory responses were observed using chromaffin cells co-loaded with Fura-2 and Rhod-2 in the perfused rat adrenal medulla. When the cells were stimulated with 40mM K<superscript>+</superscript> in the perfusate, the duration of [Ca<superscript>2+</superscript>]<subscript>m</subscript> response markedly increased with prolongation of the stimulation period, exhibiting a mean half-decay time of 21min with 30s stimulation, whereas its amplitude was not altered with stimulations of 10–30s. A computer simulation analysis showed that such a mode of [Ca<superscript>2+</superscript>]<subscript>m</subscript> response can be produced if excess Ca<superscript>2+</superscript> taken up by mitochondria precipitates as calcium phosphate (Pi) salt. In the presence of 5μM rotenone plus 10μM oligomycin, a decrease in the duration of [Ca<superscript>2+</superscript>]<subscript>m</subscript> response and a slight but significant increase (24%) in the secretory response to 30s stimulation with 40mM K<superscript>+</superscript> were observed. Simulation analyses suggested that this effect of rotenone may be due to reduction in mitochondrial Ca<superscript>2+</superscript> uptake induced by rotenone-elicited partial depolarization of the mitochondrial membrane potential. In chromaffin cells transsynaptically stimulated through the splanchnic nerve, the intensity of NAD(P)H autofluorescence changed with time courses similar to those of [Ca<superscript>2+</superscript>]<subscript>m</subscript> responses. The temporal profiles of those two responses were prolonged in a similar manner by application of an inhibitor of mitochondrial Na<superscript>+</superscript>/Ca<superscript>2+</superscript> exchanger, CGP37157. Thus, due to the unique Ca<superscript>2+</superscript> buffering mechanism, [Ca<superscript>2+</superscript>]<subscript>m</subscript> responses associated with massive mitochondrial Ca<superscript>2+</superscript> uptake may occur within a limited concentration range in which Ca<superscript>2+</superscript>-sensitive dehydrogenases are activated to control the mitochondrial redox state in stimulated chromaffin cells. [Copyright &y& Elsevier]
- Subjects :
- MITOCHONDRIA
CALCIUM
CYTOSOL
CHROMAFFIN cells
COMPUTER simulation
Subjects
Details
- Language :
- English
- ISSN :
- 01434160
- Volume :
- 39
- Issue :
- 1
- Database :
- Supplemental Index
- Journal :
- Cell Calcium
- Publication Type :
- Academic Journal
- Accession number :
- 23111512
- Full Text :
- https://doi.org/10.1016/j.ceca.2005.09.001