The Effect of Adrenergic Receptor Blockade on the Exercise-Induced Rise in Pancreatic Polypeptide in Man*

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Abstract
The effect of adrenergic receptor-blocking agents upon plasma levels of human pancreatic polypeptide (hPP), human GH (hGH), immunoreactive insulin and glucose during graded submaximal exercise was ascertained in 6 healthy non-obese males. Subjects exercised from 0-27 min on a motor-driven treadmill and received infusions from -10 to 40 min of either saline, saline plus phentolamine (0.5 mg/min; .alpha.-adrenergic blockade) or propranolol (0.08 mg/min; .beta.-adrenergic blockade). During saline-exercise, mean plasma hPP rose from a mean (.+-. SE) basal level of 45 .+-. 11 to 149 .+-. 51 pg/ml at 27 min, whereas with phentolamine-exercise, the maximal level reached by mean plasma hPP (305 .+-. 28 pg/ml) was significantly greater than that with saline (P < 0.05). During propranolol-exercise, mean plasma hPP did not rise significantly above the basal level. The incremental area under the hPP curve for phentolamine-exercise also was significantly greater than that for saline-exercise or propranolol-exercise. The changes in plasma hGH during and after saline-exercise correlated with those of hPP, but the effects of phentolamine and propranolol upon exercise-induced increases in hGH were opposite to the effects upon hPP. The exercise-induced fall in immunoreactive insulin was accentuated with propranolol and abolished with phentolamine. Submaximal exercise stimulates secretion of hPP and hGH; adrenergic mechanisms participate in exercise-induced increased secretion of hPP (.beta.-adrenergic stimulation augments secretion and .alpha.-adrenergic stimulation inhibits secretion); adrenergic effects which modulate exercise-induced secretion of hPP and insulin are in parallel but are opposite to those that modulate the secretion of hGH.