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Mitochondrial free [Ca2+] increases during ATP/ADP antiport and ADP phosphorylation: exploration of mechanisms. Biophys J 2010 Aug 09;99(4):997-1006

Date

08/18/2010

Pubmed ID

20712982

Pubmed Central ID

PMC2920628

DOI

10.1016/j.bpj.2010.04.069

Scopus ID

2-s2.0-77958171178 (requires institutional sign-in at Scopus site)   31 Citations

Abstract

ADP influx and ADP phosphorylation may alter mitochondrial free [Ca2+] ([Ca2+](m)) and consequently mitochondrial bioenergetics by several postulated mechanisms. We tested how [Ca2+](m) is affected by H2PO4(-) (P(i)), Mg2+, calcium uniporter activity, matrix volume changes, and the bioenergetic state. We measured [Ca2+](m), membrane potential, redox state, matrix volume, pH(m), and O2 consumption in guinea pig heart mitochondria with or without ruthenium red, carboxyatractyloside, or oligomycin, and at several levels of Mg2+ and P(i). Energized mitochondria showed a dose-dependent increase in [Ca2+](m) after adding CaCl2 equivalent to 20, 114, and 485 nM extramatrix free [Ca2+] ([Ca2+](e)); this uptake was attenuated at higher buffer Mg2+. Adding ADP transiently increased [Ca2+](m) up to twofold. The ADP effect on increasing [Ca2+](m) could be partially attributed to matrix contraction, but was little affected by ruthenium red or changes in Mg2+ or P(i). Oligomycin largely reduced the increase in [Ca2+](m) by ADP compared to control, and [Ca2+](m) did not return to baseline. Carboxyatractyloside prevented the ADP-induced [Ca2+](m) increase. Adding CaCl2 had no effect on bioenergetics, except for a small increase in state 2 and state 4 respiration at 485 nM [Ca2+](e). These data suggest that matrix ADP influx and subsequent phosphorylation increase [Ca2+](m) largely due to the interaction of matrix Ca2+ with ATP, ADP, P(i), and cation buffering proteins in the matrix.

Author List

Haumann J, Dash RK, Stowe DF, Boelens AD, Beard DA, Camara AK

Authors

Amadou K. Camara PhD Professor in the Anesthesiology department at Medical College of Wisconsin
Ranjan K. Dash PhD Professor in the Biomedical Engineering department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Adenosine Diphosphate
Adenosine Triphosphate
Animals
Buffers
Calcium
Calcium Signaling
Cell Respiration
Guinea Pigs
Hydrogen-Ion Concentration
Ion Transport
Magnesium
Membrane Potential, Mitochondrial
Mitochondria
NAD
Oxidation-Reduction
Phosphorylation
Ruthenium Red