Glucagon-, glicentin-, and pancreatic polypeptide-like immunoreativities in rectal carcinoids and related colorectal cells.

Three nonargentaffin rectal carcinoids have been investigated immunohistochemically. In one case most tumor cells reacted with antiglucagon sera as well as with 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 third 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. Thus, both 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. It is concluded that nonargentaffin rectal carcinoids are histogenetically linked to nonargentaffin endocrine cells of the human rectum.