Original Paper Veterinarni Medicina, 56, 2011 (6): 286–293 286 he efects of prepubertal epididymal ligation upon androgen receptor distribution in the rat caput epididymis F.M. Gur 1 , S. Timurkaan 2 , N. Timurkaan 3 1 Veterinary Border Inspection Post, Ministry of Agriculture and Rural Affairs, Istanbul, Turkey 2 Faculty of Veterinary Medicine, University of Firat, Elazig, Turkey 3 Sivrice Vocational School, University of Firat, Elazig, Turkey ABSTRACT: The aim of the present study was to investigate the androgen receptor (AR) distribution in epididy- mal cells of developing rats and the effects of prepubertal epididymal obstruction upon AR distribution in the rat caput epididymis. At 15 days of age, the young rats were divided at random into groups for epididymal ligation or sham operation. In the ligation group the corpus epididymides were ligated bilaterally; in the sham group only laparatomy was performed. Both groups were sacrificed at 21, 56, 90, 120 days. The epididymes were removed, fixed in Bouin’s fixative and embedded in paraffin wax. The tissues were sectioned at 5 μm and stained using the microwave stimulated antigen retrieval technique for immunohistochemistry. The features of the immunohisto- chemical staining of caput epididymal cells for the AR were similar across both groups. The operation did not affect AR distribution in caput epididymis. Positive immunohistochemical staining for the AR appeared in nuclei but not in the cytoplasm of caput epididymal cells at all ages beginning from 21 to 120 days old. The staining intensity of AR-positive cells did not change depending on age. In the caput epididymis, immunostainable AR were found in tubular epithelial cells (principal cells, basal cells and apical cells) and interstitial stromal cells (peritubular smooth muscle cells). There were no significant histological alterations in epididymal epithelium. Keywords: androgen receptor; immunohistochemistry; epididymal ligation; epididymis; rat The mammalian epididymis is a complex organ, whose many functions such as absorption of tes- ticular fluid or secretion of proteins, promote the maturation and storage of spermatozoa produced in the testis (Ungefroren et al., 1997). The epidi- dymis is histologically divided into three major parts: the caput, the corpus and the cauda. The caput epididymis is formed of efferent ducts and an epididymal duct. The structure of the ductus epididymis is comprised of highly coiled ducts which have a big lumen and a thick wall and lie embedded in collageneous connective tissue. The epithelium of the epididymis is composed of prin- cipal, basal, apical and clear cells (predominant in the tail of the epididymis; Ungefroren et al., 1997; Abraham and Kierszenbaum, 2007; Moonjit and Suwanpugdee, 2007). Early studies established that the epididymis requires androgens for its prenatal and postnatal differentiation (Brooks, 1979; Orgebin-Christ et al., 1996) and maintenance of epithelial structure (Maneenly, 1959). Androgens reach the epididymis via the blood supply and intraluminal fluid (Turner et al., 1984). Androgen effects are principally me- diated by the androgen receptor, a member of the steroid hormone receptor superfamily (Carson- Jurica et al., 1990). This nuclear transcription fac- tor, on binding to androgen, becomes competent for binding DNA and of stimulating androgen- dependent gene transcription (Zho et al., 1994; Bardin et al., 1996). The presence of androgen re- ceptors has been demonstrated in epididymal cells from several species using biochemical (Tindall et al., 1975; Carreau et al., 1984a,b; Tekpetey et al.,