Expression of Prolactin Receptor mRNA in Lactotrophs and Somatotrophs of the Chicken Anterior Pituitary Gland

: Prolactin (PRL) is a hormone mainly secreted by the anterior pituitary gland. In birds, PRL exerts a variety of physiological functions in target tissues expressing the PRL receptor (PRLR). In chicken, the PRLR mRNA is abundant in the anterior pituitary gland, but its regional and cellular localization are unknown. In the present study, we investigated the expression of the PRLR mRNA in cephalic and caudal lobes of the chicken anterior pituitary gland. Real-time polymerase chain reaction (PCR) revealed high levels of PRLR mRNA in both cephalic and caudal lobes. In situ hybridization revealed that the PRLR mRNA was distributed in a wide area of both lobes, and co-localized with the PRL and growth hormone (GH) mRNAs in the cephalic and caudal lobes, respectively. These results suggest that PRL exerts autocrine/paracrine effects through PRLR on PRL-producing lactotrophs and GH-producing somatotrophs in the chicken anterior pituitary gland.