Fig. 1.

An extramitochondrial acidic environment decreased oxidative phosphorylation in cardiac mitochondria. Acidification decreased ADP-stimulated oxidative phosphorylation only when glutamate + malate as complex I substrate was used (A), whereas respiration with a complex II substrate (B), a complex IV substrate (C), or a fatty acid substrate (D) were unaffected. Amobarbital (AMO), a cell-permeable, rapid and reversible inhibitor of complex I, was used in a dose response to cause a partial inhibition of complex I-driven respiration (E) that did not affect the electron transport chain distal to complex I (F). Values are means ± SE; n = 5 in each group; nAO, nanoatoms O (atomic oxygen).