Pancreatic polypeptide in cystic fibrosis.

Patients with cystic fibrosis (CF) and their normal siblings and parents were studied for protein meal-stimulated pancreatic polypeptide (PP) secretion. Patients with CF who had exocrine pancreatic insufficiency did not respond to a protein meal, whereas patients with CF and normal pancreatic function presented relatively well-preserved basal and elevated postmeal PP levels. The siblings responded with relatively lower PP levels compared with the control subjects. Plasma insulin levels were also investigated, and showed sluggish initial-phase but relatively well-preserved insulin responses in the patients with CF. Immunocytochemical and morphometric studies were made of pancreata obtained at autopsy from patients with CF. In the patients younger than 7 years of age, well-preserved islet tissue was disclosed by islet-area morphometry with normal and/or below-normal PP cell counts, whereas patients older than 9 years had relatively less insulin-containing islet tissue and scanty PP cells. Absent PP secretory response in patients with CF who had exocrine pancreatic insufficiency may suggest defects in the PP secretory mechanism. Abnormal PP secretion may be used as an indirect index of pancreatic damage in CF.