Metabolic requirements for release of endogenous noradrenaline during myocardial ischaemia and anoxia

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Abstract
1 The metabolic conditions required for noradrenaline (NA) release from ischaemic and anoxic perfused hearts of the rat were studied. 2 Forty minutes of flow reduction to approximately 0.25 ml g−1 min−1 did not elicit enhanced noradrenaline overflow from the isolated heart perfused with normoxic perfusate even in the absence of added substrate. Enhanced overflow did occur when substrate-free ischaemia was induced after a 60 min period of substrate-free perfusion. 3 Noradrenaline overflow was enhanced by perfusion at normal flow rates with an anoxic (PO2in vivo nerve-impulse independent release would be expected to occur only in regions of severe flow reduction. This may produce heterogeneous stimulation of the myocardium.