AMP-activated protein kinase (AMPK) plays a central role in influencing fuel usage and selection. The aim of this study was to analyse the impact of low-dose AMP-analogue (5 amino-imidazole-4-carboxamide-1--D-ribosyl-monophosphate [AICAR]) on whole body glucose turnover and skeletal muscle (SkM) glucose metabolism. Dogs were re-studied after prior 48 h fatty acid oxidation (FAOX) blockade by methylpalmoxirate (MP: 5 x 12 hourly 10 mg/kg doses). During the basal equilibrium period (0-150 min), fasting dogs (n=8) were infused with [3-³H] glucose, followed by either 2h saline or AICAR (1.5-2.0 mg.kg^-1.min^-1) infusions. SkM was biopsied at completion of each study. On a separate day, the same protocol was undertaken, following 48 h in vivo FA_OX blockade. The AICAR and AICAR(+ MP) studies were repeated in three chronic alloxan diabetic dogs. AICAR produced a transient fall in plasma glucose and increase in insulin, and a small decline in free fatty acid (FFA). Parallel increases in hepatic glucose production (HGP); glucose disappearance (Rd_tissue) and glycolytic flux (GF) occurred, whereas MCR_g did not change significantly. Intracellular SkM glucose, G6P and glycogen were unchanged. Acetyl CoA carboxylase (pACC~Ser221) increased by 50%. In the AICAR (+ MP) studies the metabolic responses were modified: the glucose was lower over 120 min; only minor changes occurred with insulin and FFA; HGP and Rd_tissue responses were markedly attenuated, but MCR_g and GF increased significantly. SkM substrates were unchanged but pACC-Ser221 rose by 80%. Thus, low-dose AICAR leads to increases in HGP and SkM glucose uptake, which are modified by prior FA_ox blockade.