1995 Volume 8 Issue 4 Pages 377-384
Cigarette tobacco tar, extracted from “Mild Seven” (Japan Tobacco Industries), was administered by force into the mouse stomach with or without pretreatment by subcutaneous injection of 4-nitroquinoline 1-oxide (4NQO), the incidence, size, and histopathology of the pulmonary tumors induced were studied to elucidate the effects of tobacco tar adiministered from the gastrointestinal tract on murine pulmonary tumorigenesis. One hundred and fifty ddY mice were divided into five groups; non-treated control animals, vehicle control animals treated only with intragastric injection of corn oil, tar-treated animals, 4NQO-treated animals, and 4NQO+tar-treated animals. The animals received intragastric injections of tar dissolved in corn oil at a dosage of 30 mg/kg body weight twice a day 6 days a week for 43 weeks. 4NQO was subcutaneously injected at a dosage of 8 mg/kg body weight at the first day of the experiment. The animals were sacrificed at the 52nd week. The average incidences of pulmonary tumors and adenocarcinomas per animal were 0.70 and 0.23 in the non-treated group, 0.55 and 0.31 in the vehicle control group, 0.82 and 0.61 in the tar-treated group, 2.32 and 1.00 in the 4NQO-treated group, and 2.26 and 1.33 in the 4NQO+tar-treated group, respectively. Gastrointestinal adminstration of cigarette tobacco tar did not increase the incidence of pulmonary tumors but did enhance the tumor grade from adenoma to adenocarcinoma. Thus, this study clarified that cigarette tobacco tar through the gastrointestinal tract could function as a progressive agent in pulmonary tumorigenesis.
