Stimulation of splanchnic glucose production during exercise in humans contains a glucagon-independent component

To determine the importance of basal glucagon to the stimulation of net spl anchnic glucose output (NSGO) during exercise, seven healthy males performe d cycle exercise during a pancreatic islet cell clamp. In one group (BG), g lucagon was replaced at basal levels and insulin was adjusted to achieve eu glycemia. In another group (GD), only insulin was replaced at the identical rate used in BG, and basal glucagon was not replaced. Exogenous glucose in fusion was necessary to maintain euglycemia during exercise in BG and durin g rest and exercise in GD. Arterial glucagon was at least twofold greater i n BG than in GD throughout the pancreatic islet cell clamp. Although basal NSGO remained stable in BG (2.5 +/- 0.5 mg.kg(-1).min(-1)), basal NSGO drop ped by 70% in GD (0.7 +/- 0.3 mg.kg(-1).min(-1)). NSGO was also greater in BG than in GD at 10 min of moderate exercise, most likely due to the residu al effect of basal glucagon replacement. However, NSGO increased slightly a nd remained similar throughout the remainder of moderate and heavy exercise in BG and GD. Therefore, a mechanism independent of changes in pancreatic hormones and/or the level of glycemia contributes toward modest stimulation of NSGO during moderate and heavy exercise.