Distribution and molecular forms of glucagon-like peptide in the dog

Using glucagon-like peptide-1 N-terminus and C-terminus directed antisera, we investigated concentration and molecular forms of GLP-1 immunoreactivity (IR) in extracts of various tissues of the dog. GLP-1 IR measured with C-terminus-directed antiserum R2337 (GLP-1 IR-CT) was high in the ileum, appendix, jejunum, colon, and gastric fundus and body. GLP-1 IR measured with N-terminus-directed antiserum R1043 (GLP-1 IR-NT) was high only in the pancreas, and gastric fundus and body. Only GLP-1 IR-CT was found in the hypothalamus, thalamus and medulla oblongata. No immunoreactive materials were detected in the liver, spleen and kidney. Gel-filtration with Sephadex G-50 showed two peaks of both GLP-1 IR-CT and GLP-1 IR-NT, at 10kd and at the position of GLP-1 (1–36 amide) in the pancreatic extract, and one peak at 10kd in the stomach extract. Ileal extracts showed 3 peaks of GLP-1 IR-CT at 10kd, at the position of GLP-1(1–36 amide) and GLP-1(7–36 amide), respectively, but GLP-1 IR-NT was coeluted with GLP-1(1–36 amide). Hypothalamic extracts showed a single peak at the position of GLP-1(7–36 amide). These results suggest that processing of preproglucagon differs in different organs, and that the main GLP-1-related products are a large molecular form and GLP-1(1–36 amide) or GLP-1(1–37) in the pancreas, and GLP-1(7–36 amide) or GLP-1 (7–37) in the ileum and hypothalamus.