Predominant expression of growth hormone secretagogue receptor in the caudal lobe of chicken pituitary and parallel developmental increase in expression of pituitary GH and proventriculus ghrelin mRNA
Yamamoto, I.(Nippon Veterinary and Life Science Univ., Musashino, Tokyo (Japan)) | Yoshimura, Y. | Tsukada, A. | Kansaku, N. | Tsushima, N. | Tanaka, M.
To examine the involvement of ghrelin in growth hormone (GH) synthesis in the chicken pituitary, the regional distribution of GH secretagogue receptor (GHS-R)/ghrelin receptor was investigated. Quantitative real-time polymerase chain reaction (Q-PCR) analysis revealed that the expression levels of GHS-R and GH mRNA in the caudal lobe were about fourfold and sevenfold higher in the cephalic lobe of 7 day-old chickens, respectively. Immunohistochemical analysis showed that GHS-R immunoreactivity was more abundant in the caudal lobe than in the cephalic lobe, as was the case for GH immunoreactivity. By Q-PCR, parallel increases were observed in the expression levels of ghrelin mRNA in the proventriculus and GH mRNA in the pituitary from embryonic day 17 to day 7 after hatching, whereas no significant change was found in the expression levels of GHS-R mRNA in the pituitary during this period. These results suggest that proventriculus-derived ghrelin may participate in pituitary GH synthesis by acting on its receptor during late embryonic development and the early post-hatching period in chickens.
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