Elevated plasma enteroglucagon alone fails to alter distal colonic carcinogenesis in rats

The effect of physiologic increases of plasma enteroglucagon, induced by massive bypass or resection of small bowel, on large bowel cell turnover and carcinogenesis was studied in rats in which the distal colon was isolated as a mucous fistula. After injections of azoxymethane, either 85% end-to-side jejunoileal bypass, 85% jejunoileal resection, or sham bypass was performed. Controls underwent colonic transection and resuture, azoxymethane treatment, and then sham bypass. Thirty weeks later the plasma enteroglucagon level had almost trebled after jejunoileal bypass (p less than 0.001) and almost doubled after jejunoileal resection (p less than 0.002) when compared with sham bypass; sham values did not differ from controls. The median number of tumors per rat in the distal (defunctioned) colon fell from 2 to 0 (p less than 0.05). Segmental weight fell by 45% (p less than 0.001) and crypt cell production rate by 75% (p less than 0.001). Neither tumor yield nor adaptation was affected by jejunoileal bypass or jejunoileal resection. Plasma enteroglucagon has no effect on colonic cell turnover or carcinogenesis in the absence of luminal content.