Submitted to: Poultry Science
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2004
Publication Date: March 31, 2004
Citation: Richards, M.P., Poch, S.M., McMurtry, J.P. 2004. Characterization and expression of the avian ghrelin gene [abstract]. Poultry Science. 83 (Suppl.1):191.
Ghrelin (GHR), a peptide hormone produced by the stomach in mammals, stimulates growth hormone (GH) release and food intake. Recently, GHR was identified and characterized in chicken proventriculus and shown to stimulate GH release but inhibit feed intake. The purpose of this work was to identify and characterize the GHR gene in Leghorn (LC) and broiler (BC) chickens and in turkeys (T). Using molecular cloning techniques we have sequenced cDNAs corresponding to LC and T GHR mRNAs. A total of 844 (LC) or 869 (T) bases including the complete coding regions (CDS), and the 5'- and 3'-untranslated regions (UTRs) were determined. Nucleotide sequence (CDS) predicted a 116 amino acid precursor protein for both LC and T that demonstrated complete conservation of an N-terminal 'active core' (GSSF) including a serine (position 3) known to be a modification (acylation) site important for GHR bioactivity. Additional nucleotide sequence was found in the 5'-UTRs of both LC and T cDNAs that was not present in BC. The T GHR gene, sequenced from genomic DNA templates, contained 5 exons and 4 introns, a structure similar to mammalian and chicken GHR genes. GHR was highly expressed in proventriculus with much lower levels of expression in other tissues such as pancreas, brain and intestine. RT-PCR was used to quantify GHR gene expression relative to 18S rRNA in 3 wk-old male BC. GHR expression in proventriculus increased in response to fasting but did not decline with subsequent refeeding. Plasma GHR, determined by RIA, did not change significantly in response to fasting or refeeding and did not reflect changes in proventriculus GHR gene expression. GHR expression declined in pancreas after a 48 hr fast and increased upon refeeding. Expression of the gene encoding the receptor for GHR (GH secretagogue receptor, GHS-R) was detected in pancreas possibly suggesting autocrine/paracrine effects. These results offer new insights into the avian GHR gene and the potential role of GHR in regulating feed intake and energy balance in poultry.