5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside increases myocardial glucose uptake during reperfusion and induces late pre-conditioning: potential role of AMP-activated protein kinase.

Late pre-conditioning protects against myocardial ischaemic-reperfusion injury. AMP-activated protein kinase (AMPK) is activated by exercise and 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). Early pre-conditioning involves AMPK activation and increased myocardial glucose uptake. The aim of the present study was to determine whether AICAR activates myocardial AMPK and induces late pre-conditioning and whether myocardial glucose uptake during reperfusion was modulated. Twenty-four hours after AICAR treatment or exercise, Wistar rats were subjected to ischaemia and reperfusion in a Langendorff model and compared to control rats. AMPK activity increased immediately 2.5-fold in AICAR-treated animals (P < 0.01) and twofold in exercised animals (P < 0.05). AICAR and exercise reduced infarct size by 60% and 50% (both P < 0.01), respectively, and increased myocardial glucose uptake during reperfusion (AICAR; 45%, P < 0.05, exercise; 40%, P < 0.05). In conclusion, AICAR induces late pre-conditioning and increases myocardial glucose uptake during reperfusion in rat hearts. AICAR and exercise activate AMPK, suggesting a role of AMPK in the signalling mechanisms behind late pre-conditioning.