Background: In male animal of most mammals, a rudimentary mammary structure is encountered; however the male albino rat mammary gland structure is unique in displaying marked development and showing great sexual dimorphism.
Aim of the work: Detection of causes and importance of the unique histological and serological features of adult male albino rat’s mammary gland.
Materials and methods: Twenty eight adult healthy albino rats were utilized and separated into male and female groups. Blood samples were collected for serological analysis of estradiol 17β (ERB), progesterone (PRA) and prolactin (PRL) hormones. Small pieces of the right mammary glands were submitted to tissue epidermal growth factor (EGF), insulin growth factor-I (IGF-I) and transforming growth factor-α (TGF α) analysis. Paraffin sections were prepared for histological; Hematoxylin and Eosin (H&E) and Masson’s trichrome (MT) staining and immunohistochemical stain of estrogen (ER) and progesterone (PR) receptors. The left glands were prepared for whole mount carmine alum stain technique.
Results: The male group revealed a high statistically significant decrease of PRL hormone and a statistically significant decrease of ERB hormone levels in comparison to female group. Progesterone hormone serum level showed no statistically significant difference between both groups. A statistically significant decrease regarding tissue EGF, IGF I and TGFα in male group was detected. Whole mount technique showed a remarkable glandular growth of the male mammary glands with elaborated lobulo-alveolar structure. Short thick interlobular ducts, prominent lateral buds and large terminal lobules were seen. The histological examination of male group revealed less developed stroma in the form of thin capsule and septa, thin periductal fibrous stroma. Lobulo-alveolar structures were predominant in male gland. An intense positive immunohistochemical staining of progesterone receptor was detected in some ductal and stromal cells in male MG.
Conclusion: In albino rat, the male mammary gland was well developed as female despite of the normal levels of the steroid hormones and without drug supplementation or endocrinal disturbance. This condition can provide fundamental information about a physiological type of gynecomastia that does not need hormonal replacement and may need only cosmetic surgical intervention.
Keywords: Male rat, mammary gland, growth factors, prolactin, progesterone, whole mount carmine alum