title: Histidyl-proline diketopiperazine cyclo (His-Pro): identification and characterization in rat pancreatic islets.
abstract: Measurements of cyclo (His-Pro) in the pancreas were carried out in the rat by a specific radioimmunoassay. Cyclo (His-Pro)-like immunoreactivity was identified in pancreatic islets with a mean concentration of 2023 pg/mg protein, 88-fold higher than that of the whole pancreas. Cyclo (His-Pro) immunoreactivity from pancreatic extracts was indistinguishable immunologically and chromatographically from synthetic cyclo (His-Pro). Insulin-induced hypoglycemia caused a significant, 53% decrease in pancreatic cyclo (His-Pro) concentrations, and FLA-63, a dopamine beta-oxidase inhibitor, also reduced islet cyclo (His-Pro) concentrations 51%. These data indicate that cyclo (His-Pro) is present in rat pancreatic islets and may play a potential role in modulating pancreatic responses to nutrient and pharmacologic stimuli.
mesh_terms: D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010456:Peptides, Cyclic / Q000302:isolation & purification* / Q000378:metabolism; D010879:Piperazines / Q000302:isolation & purification* / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007328:Insulin; D010456:Peptides, Cyclic; D010879:Piperazines; C015924:histidyl-proline diketopiperazine