CHARACTERIZATION OF N-ETHYL-N-NITROSOUREA INDUCED MAMMARY-TUMORS IN THE RAT

  • 1 January 1983
    • journal article
    • research article
    • Vol. 110  (2) , 161-169
Abstract
A single i.p. inoculation of 180 mg/kg N-ethyl-N-nitrosourea (ENU) into 30-day-old outbred Sprague-Dawley (CD) rats resulted in an 90% incidence of mammary tumors (MT) after an average latent period of 93 days with an 85% rate of malignancy. The incidence, induction period, number of tumors/rat, and the rate of malignancy were reduced in rats ovariectomized prior to or shortly after (5 days) ENU exposure. Over 70% of the ENU-induced MT regressed following ovarioectomy. The malignant MT developed from nodules located in the terminal end buds (TEB), which are believed to contain the most susceptible cell population for chemical carcinogens. The serum Ca was elevated above control values in 92% of intact rats evaluated with MT in the absence of bone metastases. No correlation was demonstrated between the volume of MT or total number of MT and the serum Ca level. The ENU-induced MT is a reproducible animal model that can be used in the investigation of the early changes in mammary cells (especially TEB) and the interrelationship between the carcinogen and ovarian hormones associated with neoplastic transformation.