Immunoreactive adrenocorticotropin in the gastrointestinal tract and pancreatic islets of the rat.

Radioimmunoassayable ACTH is detectable in the gastrointestinal tract and pancreatic islets of the rat by using a midportion ACTH antiserum. Portions of the gastrointestinal tract and isolated pancreatic islets were extracted with 0.1 N HCl. Serial dilutions of the extracts resulted in inhibition curves parallel with human alpha ACTH-(1-39). The highest concentrations were in the isolated pancreatic islets (20 pg/ml protein) and the gastric antrum-pylorus (17.9 +/- 1.2 pg/ml protein). Chromatographic characterization of the stomach extract showed a main peak, with an elution constant identical to that of [125I]iodo-ACTH-(1-39) and an elution pattern identical to that of rat pituitary extracts and medium from incubated rat pituitaries.