Immunohistochemical localization of somatostatin receptor SST2A in the rat pancreas

Somatostatin (SRIF) acts on specific membrane receptors to inhibit exocrine and endocrine pancreatic functions. Five SRIF receptor genes have been cloned, producing six receptor proteins (sst-s). We used a recently developed antibody to localize the sst2A splice variant in the rat pancreas. Western blots identified the sst2A receptor as an 90 kDa glycosylated protein in pancreatic tissue. In tyramide-amplified immunostainings all acinar cells, and the glucagon and pancreatic polypeptide immunoreactive cells (A and PP, respectively) were intensely labeled for sst2A, while no signal was detected in SRIF producing (D) cells. A very few insulin immunoreactive (B) cells were also labeled for sst2A, but the signal in these cells was lower than in exocrine, A or PP cells. Absorption of the sst2A antibody with the receptor peptide abolished specific staining in both immunoblots and tissue sections (negative control). These studies are the first to localize any SRIF receptor subtype in the rat pancreas. The specific localization of sst2A receptor in acinar, A and PP cells if confirmed in humans, would suggest that subtype specific analogs will be useful for the therapeutic regulation of exocrine and/or endocrine pancreatic secretion.