Modulation of symmetrical 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis by isoproterenol (IPR).

The modulatory effect of IPR on the initiation and promotion of DMH-induced colon carcinogenesis was investigated using CF-1 young adult female mice. IPR given soon after each of weekly DMH injections inhibited the initiation phase of colon carcinogenesis when the cumulative dose of DMH was small. However, such inhibition was not observed when the cumulative dose of DMH was doubled. Colon neoplasms that developed in spite of IPR treatments seemed to infiltrate the colon wall earlier as compared to those without IPR. On the other hand, IPR did not appear to affect the promotion phase of colon carcinogenesis.