There is increasing evidence that hyperglycaemia at the time of acute myocardial infarction (MI) increases the probability of mortality(1). The degree of glycaemia, rather than diabetes, has been postulated to be the cause of deleterious effects(1), including pro-arrhythmic action potential prolongation(2, 3). Our previous study identified that inhibition of PKCα and β attenuated the damaging effects of hyperglycaemia on cardiomyocytes(3). Here we present data demonstrating that inhibition of PKCα and β reveals a metabolite concentration-dependent cardioprotection. Cardiomyocytes isolated from adult male Wistar rats were subjected to a chemically mimicked ischaemia/reperfusion injury (I/R) model. Briefly, with 1 Hz of electric field stimulation cells were paced at 32±2 °C and perfused with normal Tyrode’s (NT) solution for 2 mins, followed by 7 mins with substrate-free metabolic inhibition Tyrode’s (SFT) containing 2 mM cyanide and 1 mM iodoacetic acid. Cells were then ‘reperfused’ with NT for 10 mins and the contractile recovery assessed as a measure of cardioprotection. In control rat cardiomyocytes in 5 mM glucose NT, 29±2% of cardiomyocytes recovered contractile function and 25±3% entered a hypercontracted state. In 20 mM glucose, contractile recovery was 27±3% (P>0.05) whilst hypercontracture was increased to 39±4% (P<0.01). After PKCα and β inhibition with 300 nM Gö6976 contractile recovery in 20 mM glucose NT was increased to 59±2% (P<0.001), with an EC50 glucose concentration of 12.7±1.4 mM, and hypercontracture reduced to 10±1% (P<0.01). Inhibition with LY379196 (PKCβ-specific inhibitor) also increased contractile recovery (56±3%, P<0.001) and reduced hypercontracture (14±3%, P<0.01). Replacing glucose with fructose also increased contractile recovery at 20 mM (62±2%, P<0.001, EC50 10.8±1.8 mM) and reduced hypercontracture (9±2%, P<0.001) after treatment with 300 nM Gö6976. Similar results were obtained using cell permeant (Tat-peptide linked) PKCα and β inhibitor peptides. The cardioprotection-like phenotype afforded by elevated glucose was unaffected by inhibition of PKCε using 100 nM Tat-PKCε inhibitor peptide (contractile recovery 58±3%, P<0.001). Similar results were found in guinea pig cardiomyocytes. All data tested using a one-way ANOVA and Bonferroni’s post-hoc test, n≥6 experiments, ≥93 cardiomyocytes from ≥3 animals. These data suggests that, as well as reducing pro-arrhythmic action potential prolongation; inhibition of PKCα and β in hyperglycaemic conditions may impart protection to cardiomyocytes during ischaemia. This metabolism-induced, PKCε-independent, cardioprotection may provide a useful clinical adjunct therapy for reducing the deleterious effects of hyperglycaemia during MI.