Somatostatin-28 like immunoreactivity in normal and tumour tissue from duodenum and pancreas

Radioimmunoassay using labelled somatostatin-14 revealed that components of somatostatin-28 antisera cross-reactive to somatostatin-14 were removed by absorption of somatostatin-28 antisera with sepharose 4B-somatostatin-14. Indirect immunofluorescence techniques using specific antisera against somatostatin-28 were carried out in normal pancreas, duodenum, a somatostatinoma in the duodenum, and pancreatic tumour cells containing somatostatin-14 positive cells, in order to establish if somatostatin-28 is present in normal and pathological tissues. Somatostatin-28 like immunoreactivity was present in pancreatic islets cells and in the epithelial cells of the duodenum as well as in the duodenal somatostatinoma and in pancreatic tumour cells. Furthermore, cells reacting with specific antisera against somatostatin-28 were identical to those with somatostatin-14 antisera in normal and pathological tissues. The findings suggested that somatostatin-28 like immunoreactivity may be constantly present in the tissues where somatostatin like immunoreactivity was detected using somatostatin-14 antisera. However, further studies were necessary to clarify whether somatostatin-28 and somatostatin-14 were independently present in these tissues, in other words, whether somatostatin-14 may be produced from somatostatin-28 or not, since somatostatin-14 antisera had cross-reactivities to somatostatin-28.