State 3 respiration of rat heart mitochondria decreased approximately 60% after 20 min normothermic in vitro
ischemia. After 20 min
ischemia, the levels of intramitochondrial
adenine nucleotides (
ATP +
ADP +
AMP) decreased to approximately 20% of control values, with a rapid loss between 10 and 20 min. Also, the exchangeable
adenine pool of the mitochondria decreased 60% after 20 min
ischemia. State 4 respiration was not affected by the ischemic insult. The
adenine nucleotide translocase activities of mitochondria from control and ischemic hearts were too high to measure accurately. Therefore, the effects of
ischemia on
adenine nucleotide translocase activity could not be established. However, 1 microM
carboxyatractyloside did not impair state 3 respiration of control mitochondria, but did inhibit the
adenine translocase activity by at least 80%. Moreover, titration of state 3 respiration with
carboxyatractyloside produced sigmoidal curves for mitochondria from control and ischemic tissue. State 3 respiration correlated well with the total mitochondrial
adenine nucleotides and the exchangeable
adenine pool (r = 0.63 and 0.78, respectively). Data collected from isolated perfused rat hearts also showed a good correlation between state 3 respiration and the exchangeable
adenine nucleotides (r = 0.92). In this study, mitochondria were isolated from hearts that were either perfused, made ischemic for 30 min by aortic cross-clamp, or reperfused for 10 min after the aortic cross-clamp. The slopes and y-intercepts of the regression lines were similar for the in vitro ischemic and the perfusion studies. There was no significant difference between the effects of
ischemia on the state 3 and uncoupled respiratory rates.(ABSTRACT TRUNCATED AT 250 WORDS)