Mitochondrial
F(1)F(0)-ATPase normally synthesizes
ATP in the heart, but under ischemic conditions this
enzyme paradoxically causes
ATP hydrolysis. Nonselective inhibitors of this
enzyme (
aurovertin,
oligomycin) inhibit
ATP synthesis in normal tissue but also inhibit
ATP hydrolysis in ischemic myocardium. We characterized the profile of
aurovertin and
oligomycin in ischemic and nonischemic rat myocardium and compared this with the profile of
BMS-199264, which only inhibits F(1)F(0)-ATP
hydrolase activity. In isolated rat hearts,
aurovertin (1-10 microM) and
oligomycin (10 microM), at concentrations inhibiting
ATPase activity, reduced
ATP concentration and contractile function in the nonischemic heart but significantly reduced the rate of
ATP depletion during
ischemia. They also inhibited recovery of reperfusion
ATP and contractile function, consistent with nonselective
F(1)F(0)-ATPase inhibitory activity, which suggests that upon reperfusion, the
hydrolase activity switches back to
ATP synthesis.
BMS-199264 inhibits F(1)F(0)
hydrolase activity in submitochondrial particles with no effect on
ATP synthase activity.
BMS-199264 (1-10 microM) conserved
ATP in rat hearts during
ischemia while having no effect on preischemic contractile function or
ATP concentration. Reperfusion
ATP levels were replenished faster and
necrosis was reduced by
BMS-199264.
ATP hydrolase activity ex vivo was selectively inhibited by
BMS-199264. Therefore, excessive
ATP hydrolysis by
F(1)F(0)-ATPase contributes to the decline in cardiac energy reserve during
ischemia and selective inhibition of
ATP hydrolase activity can protect ischemic myocardium.