The effect of alpha adrenergic receptor blockade on the glucagon-induced growth hormone response

The effect of a alpha adrenergic blockade (phentolamine) on glucagon induced growth hormone response was tested in five normal men. There was no significant difference in growth hormone concentrations between the glucagon test and the glucagon-phentolamine test (mean maximum level, 23.4 +/- 3.7 ng/ml and 23.1 +/- 5.9 ng/ml, respectively). Insulin secretion was significantly higher (P less than 0.025) 30 and 60 min after an injection of glucagon in the glucagon-phentolamine test. The results suggest that the stimulation of growth hormone secretion by glucagon is not mediated through an alpha adrenergic mechanism.