Development, Validation, and Utilization of a Novel Antibody Specific to the Type III Chicken Gonadotropin-releasing Hormone Receptor

Two gonadotropin-releasing hormone receptors (GnRH-Rs) have been characterized in chickens to date: cGnRH-R-I and cGnRH-R-III, with cGnRH-R-III being the predominant pituitary form. The purpose of the present study was to first validate a novel antibody for the specific detection of cGnRH-R-III and second, using this antibody, detect changes in cGnRH-R-III protein levels in the pituitary gland of male and female chickens during a reproductive cycle. The localization of cGnRH-R-III within the anterior pituitary gland was also determined. Western blotting of pituitary extracts and transiently transfected COS-7 cell lysates revealed that our antibody is highly specific to cGnRH-R-III protein. Similarly, when used in immunocytochemistry, this antibody specifically detects cells expressing cGnRH-R-III and not cGnRH-R-I. Western blot analyses of chicken pituitary gland homogenates show that cGnRH-R-III protein levels are significantly greater in sexually mature birds than in immature birds or birds at the end of a reproductive cycle (P < 0.0001). A similar pattern was observed for both males and females. Additionally, the antibody was able to detect cGnRH-R-III in cells along the periphery of the cephalic and caudal lobes of the anterior pituitary where the cells containing the gonadotropins are located. In summary, we successfully validated a novel antibody to cGnRH-R-III and showed levels of cGnRH-R-III protein in the pituitary fluctuate with respect to the reproductive status in both male and female chickens.