Somatostatin-28(1-12)-like immunoreactivity in the rat.

The distribution of the newly characterized peptide somatostatin-28(1-12) was determined in rat tissues using a radioimmunoassay in which the immune plasma is directed against the C-terminus of the dodecapeptide. In the central nervous system, somatostatin-28(1-12)-like immunoreactivity is highly concentrated in the hypothalamus and the amygdala. In the digestive system, the highest levels of immunoreactivity are found in the stomach, the pancreas and the colon. The immunoreactive material measured in different tissues is the heterogenous: in addition to the dodecapeptide, two N-terminally extended somatostatin-28(1-12) peptides of 4,400 and 8,000 mol wt are also detected by the immune plasma. However, the dodecapeptide itself usually accounts for the majority (66 to 75%) of the total somatostatin-28(1-12)-like immunoreactivity present in those tissues.