[The field of endocrinology-gastrointestinal hormones: radioimmunoassay and regulation of plasma levels].

Radioimmunoassay is still by far the most reliable tool for the measurement of plasma gastrointestinal hormones. However, various factors in plasma, without proper control, can give rise to erroneous results in radioimmunoassay. It contains 1) proteolytic enzymes which degradation the peptide 2) plasma nonspecific interference 3) cross reaction of various peptides of similar structure 4) molecular species which the antibody recognizes, and so on. We reviewed the mechanism of increase in plasma levels of pancreatic polypeptide (PP) measured by radioimmunoassay. Its secretion in the basal state as well as after meals in normal humans and dogs is governed mainly by vagal cholinergic mechanism. However, bile acid and other gastrointestinal hormones (Insulin and CCK) play a part in the postprandial PP response in experimentally induced diabetic and total biliary diversion dogs. The production of hydrochloric acid or secretin is not requisite for plasma PP response to an ingested meal.