1. Somatostatin-28(1-12)-like immunoreactivity in the rat
R Benoit, N Ling, C Bakhit, J H Morrison, B Alford, R Guillemin Endocrinology. 1982 Dec;111(6):2149-51. doi: 10.1210/endo-111-6-2149.
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.
2. Somatostatin-28 [1-12]-like peptides
R Benoit, P Bohlen, N Ling, F Esch, A Baird, S Y Ying, W B Wehrenberg, R Guillemin, J H Morrison, C Bakhit Adv Exp Med Biol. 1985;188:89-107. doi: 10.1007/978-1-4615-7886-4_6.
The search for a peptide corresponding to the NH2-terminus of somatostatin-28 (SS-28) in tissues has led to the isolation and characterization of somatostatin-28[1-12] from pancreas and hypothalamus. Somatostatin-28[1-12]-like immunoreactivity [SS-28 [1-12]-LI] is widely distributed throughout the central nervous system and the digestive system of rodents and primates, reaching levels comparable to those of somatostatin-14 (SS-14). Antibodies directed against the C-terminal end of the dodecapeptide are more specific and constitute excellent markers for the "prosomatostatin" system in mammalian tissues. In rat brain, SS-28[1-12]-LI material is highly concentrated in nerve fibres and terminals, especially in the median eminence, layer I of neocortex, the outer molecular layer of the dentate gyrus and the striatum. Additionally, immunoreactivity is observed in large multipolar or occasionally pyramidal-like neurons of the neocortex. SS-28[1-12] is secreted from hypothalamus and amygdala by a calcium dependent mechanism. No biological role is presently known for the dodecapeptide. Two other peptides of Mr = 8000 (8 K) and Mr = 5000 (5 K) which contain SS-28[1-12] at their carboxy-termini are present in acid extracts from rat pancreas, brain and spinal cord. These two peptides were isolated from an acid extract of rat brains using ion-exchange chromatography, gel permeation chromatography and reverse-phase HPLC. Results from amino acid analysis and partial sequencing were compared to the sequence of the cDNA encoding rat pre-prosomatostatin (prepro-SS) and revealed that the 8 K peptide is a 76 amino acid molecule corresponding to prepro-SS[25-100] and that the 5K peptide, which contains 44 amino acids, corresponds to prepro-SS [57-100]. The 5 K peptide was generated after cleavage of a Leu-Leu bond at position 56-57 of prepro-SS. The four most predominant peptides of the "prosomatostatin system" presently characterized are: SS-14, SS-28[1-12], SS-28 and prepro-SS[25-100]. Studies on pooled perfusates from rat hypothalamic tissue show that prepro-SS[25-100] is released with SS-28[1-12] in vitro and accounts for 22% of the total SS-28[1-12]-like immunoreactive material released during depolarization. The 5 K peptide is apparently not secreted. The presence of prepro-SS[25-100] in brain implies that, first, prosomatostatin can serve as an immediate precursor for SS-14 without going through SS-28 as an intermediate step and second, other peptides could conceivably be derived from the cryptic portion of the precursor.
3. Distribution of somatostatin-28 (1-12), calcitonin gene-related peptide, and substance P in the squirrel monkey brainstem: an immunocytochemical study
E Duque-Díaz, R Coveñas Anat Sci Int. 2019 Jan;94(1):86-100. doi: 10.1007/s12565-018-0453-y. Epub 2018 Jul 26.
Using an immunocytochemical technique, we have studied the distribution of fibers and cell bodies containing somatostatin-28 (1-12) [SOM-28 (1-12)], calcitonin gene-related peptide (CGRP), and substance P (SP) in the brainstem of Saimiri sciureus. The distribution of the peptidergic cell bodies was very restricted: perikarya containing SOM-28 (1-12) were only observed in the substantia grisea centralis, while no immunoreactive cell bodies containing CGRP or SP were visualized. Fibers containing SOM-28 (1-12), CGRP, or SP were widely distributed in the brainstem: immunoreactive fibers containing SOM-28 (1-12) showed the most widespread distribution and were the most abundant. The distribution of SOM-28 (1-12)-, CGRP- or SP-immunoreactive fibers was very similar. Colocalization of immunoreactive fibers containing SOM-28 (1-12), CGRP or SP was observed in many brainstem nuclei. A neuroanatomical relationship between CGRP- and SP-immunoreactive fibers was observed, although this relationship was less marked for SOM-28 (1-12) and SP and lower still for SOM-28 (1-12) and CGRP. The widespread distribution of the peptidergic fibers suggests that the studied neuropeptides are involved in many physiological actions.
