Effect of medroxyprogesterone acetate on the response of the rat mammary gland to carcinogenesis

ABSTRACT In order to determine whether mammary gland differentiation, which is known to protect this organ from chemically induced carcinogenesis, can be stimulated in virgin rats by

administration of a progestagenic agent, medroxyprogesterone acetate (MPA) was given to 300 Sprague-Dawley virgin rats, which at the ages of 45, 55, 65 and 75 days, groups I, II, III and IV

respectively, had implanted an MPA pellet of 0.5 mg (low dose-LD) or 5.0 mg (high dose-HD). Pellets were removed after 21 days, and 21 days later five animals per group were killed for

evaluation of mammary gland development. The remaining animals received 8 mg 7,12-dimethylbenz(a)-anthracene (DMBA) per 100 g body weight, and were killed after 24 weeks for evaluation of

tumour incidence. Both age and treatment affected mammary gland structure and had a significant interaction in the proportion of terminal end buds (TEBs) present. The number of TEBs

decreased as a function of age; treatment at both LD and HD did not modify the proportion of TEBs in groups I and III; LD decreased their percentage in group II, and both doses markedly

increased TEB percentage in group IV animals. MPA LD treatment did not affect overall tumour and adenocarcinoma incidence although group IV animals developed greater incidences than their

respective controls. MPA HD treated rats were 2.45 times more likely to develop tumours than their respective controls. Adenocarcinoma incidence had a significant positive correlation with

the percentage of TEBs present. It was concluded that this progestagenic agent did not increase the risk of carcinoma development when administered to virgin rats at the clinical dose used

for contraception. However, a 10-fold dose increase resulted in a higher tumorigenic response. Access through your institution Buy or subscribe This is a preview of subscription content,

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IN THE FEMALE REPRODUCTIVE SYSTEM SPONTANEOUSLY DEVELOP ENDOMETRIAL TUMOUR MASSES Article Open access 23 April 2021 ORAL ADMINISTRATION OF E-TYPE PROSTANOID (EP) 1 RECEPTOR ANTAGONIST

SUPPRESSES CARCINOGENESIS AND DEVELOPMENT OF PROSTATE CANCER VIA UPREGULATION OF APOPTOSIS IN AN ANIMAL MODEL Article Open access 13 October 2021 MIMICKING WOMEN’S ENDOCRINE MILIEU IN MICE

FOR WOMEN’S HEALTH-RELATED STUDIES Article Open access 22 February 2025 AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Pathology, Michigan Cancer Foundation, Detroit, 48201 IH

Russo Authors * IH Russo View author publications You can also search for this author inPubMed Google Scholar * P Gimotty View author publications You can also search for this author

inPubMed Google Scholar * M Dupuis View author publications You can also search for this author inPubMed Google Scholar * J Russo View author publications You can also search for this author

inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Russo, I., Gimotty, P., Dupuis, M. _et al._ Effect of medroxyprogesterone

acetate on the response of the rat mammary gland to carcinogenesis. _Br J Cancer_ 59, 210–216 (1989). https://doi.org/10.1038/bjc.1989.43 Download citation * Issue Date: 01 February 1989 *

DOI: https://doi.org/10.1038/bjc.1989.43 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not

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