HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by French, M. C. Articles by Tisdall, D. J. Search for Related Content PubMed PubMed Citation Articles by French, M. C. Articles by Tisdall, D. J.

Growth hormone and ghrelin receptor genes are differentially expressed between genetically lean and fat selection lines of sheep

AgResearch Invermay, Private Bag 50034 Mosgiel, New Zealand

¹ Corresponding author: michelle.french{at}agresearch.co.nz

The objective of this study was to determine whether differences in mRNA levels of key pituitary genes that regulate GH production, pituitary development, and growth were present and/or associated with divergent body composition phenotypes observed between sheep from genetically divergent lean and fat selection lines. Real-time PCR transcription profiles for pituitary specific transcription factor 1, prophet of pit1, GH, GH receptor, GH secretagogue receptor, GHRH receptor, leptin receptor, and somatostatin receptors 1 and 2 were determined in pituitary tissue. There was a difference in the amount of both GH (P < 0.001) and GH secretagogue receptor (P < 0.001) mRNA between the selection lines (5 females and 5 males per line; 20 wk of age); the lean line had greater abundance than the fat line, irrespective of which endogenous control gene was used. The results obtained for GHRH receptor were equivocal but suggestive; there were greater GHRH receptor mRNA levels (P < 0.001) in the lean line using beta-2-microglobulin as the endogenous control but not when hypoxanthine phosphoribosyltransferase and glyceraldehyde-3-phosphate dehydrogenase were used. No difference in pituitary specific transcription factor 1, prophet of pit1, GH receptor, leptin receptor, or somatostatin receptors 1 and 2 mRNA concentration was observed between the lines. The greater abundance of GH mRNA in the pituitary somatotropes from genetically lean animals appears to be associated with increased levels of GH secretagogue receptor mRNA and possibly GHRH receptor mRNA. This suggests that the difference in GH secretion between the lines may be due to differences in the afferent signals, such as ghrelin and/or GHRH, arising from the hypothalamus, or as a result of differential pituitary sensitivity to these hormones.

Key Words: growth hormone • growth hormone secretagogue receptor • lean and fat selection lines • pituitary • real-time polymerase chain reaction • sheep