GLUCAGON-LIKE, GLICENTIN-LIKE, AND PANCREATIC POLYPEPTIDE-LIKE IMMUNOREACTIVITIES IN RECTAL CARCINOIDS AND RELATED COLORECTAL CELLS

Abstract

Three nonargentaffin rectal carcinoids were investigated immunohistochemically. In one case, most tumor cells reacted with antiglucagon sera, antiglicentin, antibovine pancreatic polypeptide (BPP) and antihuman pancreatic polypeptide (HPP) sera; they were identified ultrastructurally as L cells. Another case showed glucagon-, glicentin- and BPP-immunoreactive cells but lacked HPP immunoreactivity. In the 3rd case, glucagon- and glicentin-immunoreactive cells were well represented, while PP immunoreactivities were scarce. Parallel investigations of human rectal and sigmoid mucosa showed numerous cells reacting with glucagon, glicentin and BPP antisera, most of which lacked HPP immunoreactivity. Cells reacting with glucagon and glicentin antisera, while lacking PP immunoreactivities, were also found. Tumor and nontumor cells produce glucagonlike immunoreactive (GLI) peptides, one of which may be glicentin or a related molecule, as well as PP-related sequences, although differing histochemically and ultrastructurally from glucagon or PP cells of the human pancreas. Nonargentaffin rectal carcinoids are histogenetically linked to nonargentaffin endocrine cells of the human rectum.