Ghrelin, a 28-amino acid acylated peptide, was identified as the endogenous ligand for the growth hormone (GH) secretagogue receptor and its role in reproduction has recently been established. It is believed that the site of ghrelin expression in testes may indicate its role in local regulation. This study investigated the immunohistochemical (IHC) localization of ghrelin in Holstein bull testis using a monoclonal anti-ghrelin antibody as primary antibody and donkey anti-rabbit IgG horseradish peroxidase (HRP) polyclonal antibody as secondary antibody. Samples of testis were collected from three Holstein bulls aged of 1.5 to 2 years old and preserved in 10% formalin for posterior inclusion in paraffin. Histological sections with 5 micron in thickness were prepared for IHC. Immunoreactions were assessed for spermatogenic cells and leydig and sertoli cells. It is believed that the site of ghrelin expression in the spermatogenesis process, leydig and sertoli cells, may indicate its role in local regulations. This is one of the first studies to provide molecular evidence for the presence of ghrelin within testicular tissue cells of Holstein bulls. پرونده مقاله