Vitamin D3 and androgen receptors in testis and epididymal region of roosters (Gallus domesticus) as affected by epididymal lithiasis

Epididymal lithiasis is a dysfunction characterized by formation of calcium-rich stones in the epididymal region of roosters, associated with decreased serum testosterone and loss of fertility. The segment most affected by the lithiasis is the efferent ductules, which, in birds, are responsible for reabsorption of calcium and luminal fluid. Therefore, we postulated that epididymal lithiasis could result from local impairment of calcium or fluid homeostasis, culminating in initiation of stone formation. Transepithelial calcium transport depends on vitamin D3 and vitamin D3 receptor (VDR). Based on the fact that VDR are present in efferent ductules, possible changes in the pattern of VDR in roosters affected by the epididymal lithiasis was investigated, to start to gain an understanding of the molecular mechanisms involved in the development of calcium stones. To evaluate the potential impact of androgen reduction, changes in androgen receptor (AR) were also investigated. Both VDR and AR were increased in specific segments of the epididymal region, whereas no alterations were found in the testes of affected animals. The increase in VDR was most likely due to an increase in the number of VDR-positive mononuclear leukocyte infiltrates found in the connective tissue followed by an increase in epithelial receptors. The AR were increased, however, mainly in the epididymal duct epithelium. These results suggest that the vitamin D3 and androgen responsive system may be directly/indirectly involved in the development of the disease.