[Immunohistochemical demonstration of somatostatin-28 like immunoreactivity in the fetal and adult human gut and pancreas].

In order to examine whether somatostatin-28 originally isolated from porcine and ovine tissues was present in the human gut and pancreas or not, immunohistochemical methods using specific antisera against somatostatin-28 and somatostatin-14 antisera were carried out in the fetal and adult human gut and pancreas. The specific antisera against somatostatin-28 were prepared from somatostatin-28 antisera by absorption of somatostatin-28 antisera with sepharose 4B-somatostatin-14. Somatostatin-like immunoreactivity appeared in the epithelial endocrine-like cells of the gut and in the pancreatic islet cells at 11 week's gestation, and thereafter it was constantly present in the fetal and adult gut and pancreas. Although detection of somatostatin-28 like immunoreactivity was not inhibited in the sections in which specific antisera against somatostatin-28 pretreated with either somatostatin-14 or other kinds of peptide hormones were employed to replace primary antisera in the immunohistochemical staining process, it was completely inhibited after use of the specific antisera against somatostatin-28 absorbed with somatostatin-28. This finding suggested that detection of somatostatin-28 like immunoreactivity was due to the immunohistochemical reaction between specific antisera against somatostatin-28 and somatostatin-28 itself. Furthermore, observation of serial sections stained by using specific antisera against somatostatin-28 and somatostain-14 antisera revealed that cells reacting with the former antisera were identical to those reacting with the latter one. Although the finding seemed to imply that full sequences of somatostain-28 may be present in the human gut and pancreas, it remained obscure whether or not somatostatin-28 and somatostatin-14 like immunoreactivities may be present independently in the cells since somatostatin-14 antisera have a crossreactivity to somatostain-28.