Catecholamines and Pancreatic Hormones during Autonomic Blockade in Exercising Man

Abstract

The importance of autonomic nervous activity for the pancreatic hormonal response to exercise in man was studied. Seven men ran at 58% of .ovrhdot.VO2 max (determined without administration of drugs) to exhaustion during .alpha.-adrenergic blockade with phentolamine (P), during parasympathetic blockade with atropine (A), or without drugs (C). At rest phentolamine increased the plasma concentrations of both insulin and norepinephrine. During exercise norepinephrine concentrations increased and were in P experiments 3 times the concentrations in C experiments. Insulin always declined during exercise but in P experiments never decreased below basal levels. At identical times neither glucagon nor glucose differed significantly in the different experiments. During exercise .alpha.-adrenergic blockade increased insulin concentrations but did not diminish the glucagon response. This response was not increased when .beta.-receptor stimulation in P experiments was intensified by the particularly high catecholamine concentrations. The concentrations of FFA, glycerol and lactate were highest in P experiments and identical in A and C experiments. During prolonged moderate exercise in man insulin secretion is depressed by stimulation of .alpha.-adrenergic receptors whereas glucagon secretion is not influenced by adrenergic receptors. Stimulation of .beta.-adrenergic receptors enhances lipolysis but neither lipolysis nor pancreatic hormonal secretion is influenced by cholinergic activity during exercise.