Triamterene Suppresses Bombesin‐enhanced Peritoneal Metastasis of Intestinal Adenocarcinomas Induced by Azoxymethane

The effects of combined administration of bombesin and the diuretic triamterene on the incidence of peritoneal metastasis of intestinal cancers induced by azoxymethane (AOM) and the labeling index of intestinal cancers were investigated in male inbred Wistar rats. From the start of the experiment, rats were given weekly s.c. injections of AOM (7.4 mg/kg body weight) for 10 weeks and s.c. injections of bombesin (40 μg/kg body weight) every other day, and from week 16, s.c. injections of triamterene (10 and 20 mg/kg body weight) every other day until the end of the experiment in week 45. Bombesin significantly increased the incidence of intestinal tumors and cancer metastasis to the peritoneum in week 45. It also significantly increased the labeling index of intestinal cancers. Although administration of both doses of triamterene with bombesin had little or no influence on the enhancement of intestinal carcinogenesis by bombesin, or the location, histologic type, depth of invasion, or labeling index of intestinal cancers, it significantly reduced the incidence of cancer metastasis. These findings indicate that triamterene suppresses cancer metastasis through a mechanism that does not affect the proliferation of intestinal cancers.