Immunolocalization of Androgen Receptor, Aromatase Cytochrome P450, Estrogen Receptor Alpha and Estrogen Receptor Beta Proteins during the Breeding Season in Scent Glands of Muskrats (Ondatra zibethicus)

Aromatase cytochrome P450 (P450arom) is an enzyme that catalyzes the conversion of androgen to estrogen. Expression of P450arom in extra-gonadal sites and locally-synthesized estrogen play an important role in physiological conditions. The purpose of this study was to investigate the cellular immunolocalization of androgen receptor (AR), P450arom, estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta) in muskrat scent glands during the breeding season. Histological observation and immunohistochemistry of AR, P450arom, ER alpha and ER beta were performed in the muskrat scent glands. In addition, total proteins were extracted from scent glandular tissues in the breeding season and were used for Western blotting analysis for AR, P450arom, ER alpha and ER beta. Histologically, glandular cells, interstitial cells, epithelial cells of the excretory duct and the excretory tubules were identified in the muskrat scent glands during the breeding season. AR was only observed in glandular cells of scent glands; P450arom was expressed in glandular cells and epithelial cells of the excretory duct; ER alpha was found in glandular cells, interstitial cells and epithelial cells of the excretory duct, whereas ER beta was present in glandular cells and epithelial cells of the excretory duct. Also, the positive signals of AR, P450arom, ER alpha and ER beta by Western blotting were all observed in scent glandular tissues. These results suggested that the scent gland is the target organ of androgens and estrogens, and that estrogens may play an important autocrine or paracrine role in glandular function of the muskrats.