Effect of phentolamine on the insulin, glucagon, and glucose responses to exercise in adrenal-denervated sheep.
Hyperglycemia and increased hepatic glucose output are characteristic responses to exercise in sheep. They appear to be due in part to alpha-adrenergic stimulation. To delineate the contributions of sympathetic innervation and adrenal catecholamines to the hormonal and metabolic responses to exercise, adrenal-denervated sheep were exercised with and without alpha-blockade (phentolamine treatment). Alpha blockade exaggerated the hyperinsulinemia during exercise (increment of 61 +/- 8 vs. 34 +/- 7 microU/mL for the control). This was associated with a reduction in glucose appearance (increments of 63 +/- 8 vs. 236 +/- 23 mumol/min, respectively). The metabolic clearance rates were not altered by alpha-blockade. It appears that both the adrenal catecholamines and adrenergic innervation to the pancreas contribute to the prevention of a rise in insulin concentrations during exercise in sheep. While this may not be essential for glucose appearance to rise during exercise, it appears necessary for an optimal response.
D000311:Adrenal Glands / Q000294:innervation*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D003714:Denervation; D005934:Glucagon / Q000097:blood*; D007328:Insulin / Q000097:blood*; D010646:Phentolamine / Q000494:pharmacology*; D005082:Physical Exertion; D012756:Sheep; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D005934:Glucagon; D010646:Phentolamine