The effects of in ovo rhIGF-I administration on expression of the growth hormone secretagogue receptor (GHSR) during chicken embryonic development.
Growth hormone secretion is under the control of a pair of hypothalamic factors, growth hormone releasing hormone and somatostatin. The growth hormone secretagogue receptor (GHSR) and its endogenous ligand represent a novel third method regulating the release of growth hormone. Early chicken embryonic development has been proposed to be independent of GH. However, recent evidence shows that peripheral GH secretion has paracrine/autocrine functions during embryonic development. In the current study, we used the reverse-transcriptase polymerase chain reaction to determine the expression pattern of the GHSR during embryonic development and the effects of in ovo recombinant human (rh) IGF-I administration on its expression pattern. Eggs were injected once with 100 ng rhIGF-I in 10 mM acetic acid, and 0.1% BSA per embryo on embryonic day 3. Total RNA was isolated from whole embryos on embryonic day (E) 0-6 (n=6 per day), thoracic/abdominal halves of the embryos on E7- E8 (n= 6 per day) and Pectoralis muscle on E9-E20 (n= 4 per day). We found that GHSR expression was low during E0-E4, followed by an increase on E5 and remained constant through E17. GHSR expression then increased on E18 before reducing on E20. A similar pattern was found in the rhIGF-I treated embryos with the exception of a significant increase in GHSR expression on E8. These data indicate that the GHSR may be active in regulating GH secretion during early embryonic development, and upregulation of the GHSR gene following IGF-I administration may have an important role in the determination of postnatal muscle growth.
Division of Animal and Veterinary Sciences, Davis College of Agriculture, Forestry and Consumer Sciences, West Virginia University, Morgantown, WV 26506, USA.
Scott A
SA
Gahr
Hakan
H
Kocamis
Jennifer J
JJ
Richter
John
J
Killefer
D000818:Animals; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D010369:Pectoralis Muscles / Q000254:growth & development / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D054440:Receptors, Ghrelin; D011994:Recombinant Proteins / Q000494:pharmacology; D012044:Regression Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D043562:Receptors, G-Protein-Coupled; D054440:Receptors, Ghrelin; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I