This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kledzik, G. S. Articles by Meites, J. Search for Related Content PubMed PubMed Citation Articles by Kledzik, G. S. Articles by Meites, J.

Reduction of Carcinogen-induced Mammary Cancer Incidence in Rats by Early Treatment with Hormones or Drugs¹

Department of Physiology, Michigan State University, East Lansing, Michigan 48824

Hormones or drugs that either elevated levels of female steroid hormones (estradiol benzoate, progesterone, or a combination of estradiol benzoate and progesterone) or of prolactin (haloperidol), or reduced estrogen activity (MER-25) or prolactin secretion (L-dopa) were injected for 20 days before and 20 days after a single i.v. injection of 7,12-dimethylbenz(a)anthracene into 60-day-old female Sprague-Dawley rats. Each treatment decreased the incidence of mammary cancers. The most effective agents were the female steroid hormones, with no mammary cancers appearing in the rats given the combination of estrogen and progesterone. These early treatments with the hormones or drugs are believed to protect the mammary tissues of the rat against the carcinogen by promoting or by inhibiting normal growth of the mammary epithelium during a period of optimal sensitivity to 7,12-dimethylbenz(a)anthracene.

¹ Supported in part by NIH Research Grant CA 10771 from the National Cancer Institute and Grant AM 04784 from the National Institute for Arthritis and Metabolic Diseases.

Received 7/ 3/74. Accepted 8/ 8/74.