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

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.

Coinfection of laboratory rats with Mycoplasma pulmonis and Chlamydia pneumoniae.

Routine examinations of conventional outbred Wistar rats in our laboratory showed increased serum levels of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and urea. Electron microscopy and specific reactions showed C. pneumoniae and M. pulmonis in lung, liver, spleen, heart, and kidney sections. We could not exclude the fact that other infectious microorganisms detected through routine health surveillance affected the Wistar rat colony; however, we have not identified any of those microorganisms by electron microscopy of the organs listed. Natural coinfection of C. pneumoniae and M. pulmonis can occur in laboratory rats and is associated with histopathological and functional compromise of many organs. Further studies comparing different conventional animals and specific pathogen-free animals are necessary to better understand the present findings and to define whether coinfection influences the results of experimental studies with rats.