Immunohistochemical localization of HCA2 receptors in reproductive system of male rats

The study investigates presence and localization of hydroxy-carboxylic acid receptor 2 (HCA2 receptor) protein in different parts of reproductive system of male rats by using immunohistochemical approach. Right lung (as positive control), testes, epididymis (head, body and tail), vas deferens and penis as well as accessory glands including vesicular gland, coagulating gland, preputial gland, gland of vas deferens and ventral prostate of six adult male Sprague Dawley rats were immediately removed after euthanasia. Transverse sections were made for immunohistochemical evaluation by using rabbit polyclonal antibody against rat HCA2 receptor as the primary antibody and mouse polyclonal anti-rabbit IgG (HRP-conjugated) as secondary antibody. In testes, spermatogenic cells, except for spermatogonia which moderately stained, showed no reactivity as well as Sertoli cells and spermatozoa. In interstitial tissue Leydig cells demonstrated receptor expression with strong intensity. Epithelial cells of epididymis showed no reactivity. Epididymal spermatozoa were also unstained. No reactivity was observed in columnar pseudo stratified epithelium of vas deferens. In penile tissue, only ciliated pseudo stratified epithelium showed a very weak reactivity. In coagulating gland, epithelial cells were moderately stained. Ciliated pseudo stratified epithelium of vesicular gland was weakly positive. No or very weak reactivity was observed in epithelial cells of preputial gland as well as pseudo stratified epithelium of prostate and gland of vas deferens. Smooth muscle cells in different parts showed weak reactivity. HCA2 receptors are present only in some cells of reproductive system of male rats especially Leydig cells and their presence and relative density is cell-type specific