Effect of cholinergic and adrenergic blockade on human pancreatic polypeptide secretion in healthy subjects.

The effect of cholinergic, alpha-adrenergic, and beta-adrenergic blockade on human pancreatic polypeptide (HPP) release has been tested in six normal subjects before and after a meal. The response to food was abolished by atropine and significantly enhanced by phentolamine and propranolol. The increase induced by phentolamine occurred during the primary phase 0-60 min after food, and that caused by propranolol was observed during the secondary phase 60-120 min postprandially. A radioimmunoassay for HPP, evaluated by accepted criteria of reliability, is described. Various fractions of the 125I-BPP tracer peak have been evaluated. Those of the central portion proved to be superior to the others because of the constant immunoreactivity and the constant incubation damage during the observation period. Serum and plasma samples were subject to different conditions of preservation before analysis of HPP. It is concluded that preservation with aprotinin heparin, collection in chilled tubes, or instant centrifugation and freezing does not improve the stability of HPP after sampling. The present study confirms a positive correlation between age and fasting HPP concentrations (R = 0.15, p = 0.05), but no difference in HPP levels between men and women has been demonstrated.