RELATIONSHIP OF COLONIC MUCOSAL BACKGROUND TO NEOPLASTIC PROLIFERATIVE ACTIVITY IN DIMETHYLHYDRAZINE-TREATED MICE

  • 1 January 1981
    • journal article
    • research article
    • Vol. 41  (7) , 2616-2620
Abstract
Proliferative activity of background and neoplastic colonic mucosa was examined following 5 mo. of weekly injections of 1,2-dimethylhydrazine (20 mg/kg) and 1 or 4 mo. of rest. The study was undertaken to determine whether previously reported changes result from an acute or chronic effect of dimethylhydrazine, and whether differences exist between stages of neoplasia. To determine whether neoplasia is responsive to a proliferative stimuls, 1,2-dimethylhydrazine dihydrochloride-treated mice were inoculated with Citrobacter freundii. The labeling index and the proliferative zone increased in background mucosa after 1 mo.; after 4 mo. labeling index, proliferative zone and crypt heights increased but the mitotic index decreased. There was a positive linear correlation between advancing tumor grade and increasing tumor labeling index, and mitotic index. Background labeling index had no effect upon tumor labeling index. Mitotic index diminished in background and neoplastic mucosa following prolonged rest and increased in both following C. freundii inoculation. 1,2-Dimethylhydrazine dihydrochloride causes long-term changes in background mucosa that are apart from a reparative response to cytotoxicity. As tumors progress, labeling index and mitotic index increase, suggesting a multistage process of evolution.