Premium
Excess Ca 2+ enhances ROS generation from inhibited complex III with FADH 2 ‐linked substrate but not NADH‐linked substrate
Author(s) -
Aldakkak Mohammed,
Stowe David F,
Dash Ranjan K,
Riess Matthias L,
Camara Amadou KS
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.639.6
Subject(s) - substrate (aquarium) , chemistry , biology , ecology
Mitochondrial complex III of the electron transport chain is a major source of ROS during ischemia. Several mechanisms modulate ROS production including mitochondrial Ca 2+ uptake. Here we tested effects of added buffer CaCl 2 on ROS generation from complex III in the presence of pyruvate (complex I linked substrate) or succinate (complex II linked substrate). Guinea pig heart mitochondria were suspended in respiration media containing amplex red and horseradish peroxidase to measure the rate of H 2 O 2 generation. Increasing concentrations of buffered CaCl 2 were added to the mitochondrial suspension. Pyruvate (10 mM) or succinate (10 mM) with rotenone (to block reversed electron flow, 10 μM) was added followed by antimycin A (5 μM) to block complex III and enhance ROS generation. Increases in CaCl 2 (0, 25, 50, 100 μM) in the respiratory buffer did not increase H 2 O 2 generation from complex III with pyruvate (436, 431, 474, 488 pM/s). In contrast, H 2 O 2 generation from complex III in the presence of succinate increased (473, 437, 526, 7202 pM/s) with increasing concentrations of CaCl 2 . Adding CaCl 2 to mitochondria enhances H 2 O 2 generation from inhibited complex III only when electrons are fed through complex II. This emphasizes the impact of matrix Ca 2+ loading on free radical formation from complex III and may point towards a more significant role of complex II in ROS generation from complex III during ischemia.