Morphometric evaluation of effects of two sex steroids on mammary gland of female rats

Abstract

Objective: The purpose of this study was to evaluate the effects of two sex hormones on normal mammary gland of female rats.

Methods: Forty 250-day-old female rats, 20 of them with offspring and 20 not, were ovariectomized and, divided into 4 subgroups in order to receive one of the following subcutaneous treatment: estradiol benzoate (EB), medroxyprogesterone (MPA), EB+MPA or placebo, for 10 weeks. After treatment, mammary glands were studied with optical microscope. Whole gland, lobule, ductule and lumen compartments were evaluated by morphometric methods. Also a qualitative evaluation were performed seeking for secretion, microcalcification and trophic status.

Results: It was found that (a) MPA-only and placebo were similar for all parameters; (b) the same between EB and EB+MPA; (c) EB and EB+MPA increased lobule, ductule and lumen compartments significantly compared to MPA-only or placebo; (d) EB increased epithelium but without significance and EB+MPA increased it significantly compared to placebo or MPA; (e) EB and EB+MPA incremented secretion.

Conclusions: In normal mammary gland of female rats: progestin action depends on estrogen presence. MPA does not revert estrogen-dependent proliferation, but it magnifies estradiol effect. Both EB and EB+MPA stimulate differentiation. Rats without offspring presented a greater epithelial proliferation under treatment with these sex hormones.