title: Evidence for the presence of dihydro (reduced) somatostatin-14 in the guinea pig brain.
abstract: Analysis of somatostatin-like immunoreactivity (SLI) in guinea pig brain by HPLC and radioimmunoassay revealed an unexpected peak of SLI eluting at a retention time slightly later than standard somatostatin-14. The following evidence argues that this peak represents dihydro (H2) somatostatin-14. (1) The peak had the same retention time as standard [H2]somatostatin. (2) The possibility of a reduction artefact due to tissue processing was excluded by adding exogenous somatostatin-14 or 125I-labeled N-Tyr-somatostatin-14 to tissue and observing that no corresponding reduced peptides were generated. (3) Mild oxidation of brain extracts with H2O2 decreased, whereas mild reduction with dithiothreitol increased, the proposed peak of [H2]somatostatin. (4) Reaction of tissue extracts with iodoacetamide decreased the size of the proposed [H2]somatostatin peak but resulted in generation of a new peak co-eluting with standard carboxymethylated somatostatin-14. The proportion of the [H2]somatostatin peak in five brain regions, the hypothalamus, amygdala, cerebral cortex, brainstem and cerebellum, ranged from 6 to 20% of total SLI. The probability of somatostatin-14 existing endogenously in reduced or oxidized forms may have implications for its biological function in the guinea pig.
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002851:Chromatography, High Pressure Liquid; D006168:Guinea Pigs; D008297:Male; D011863:Radioimmunoassay / Q000379:methods; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000032:analysis; D014018:Tissue Distribution
chemical_list: C016385:dihydrosomatostatin; D013004:Somatostatin