Regulation of the Pituitary Growth Hormone-Releasing Hormone Receptor in Ageing Male and Female LOU Rats: New Insights into Healthy Ageing

Ageing is characterised by a decrease of somatotroph functionality, involving growth hormone‐releasing hormone receptor (GHRH‐R). The present study was conducted in LOU/C/jall (LOU) rats, a strain described as a model of healthy ageing, which is characterised by a low adiposity and long life expecta...

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Published in:Journal of neuroendocrinology Vol. 17; no. 11; pp. 691 - 700
Main Authors: Veyrat-Durebex, C., Alliot, J., Gaudreau, P.
Format: Journal Article
Language:English
Published: Oxford, UK Blackwell Science Ltd 01-11-2005
Blackwell Science
Wiley Subscription Services, Inc
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Summary:Ageing is characterised by a decrease of somatotroph functionality, involving growth hormone‐releasing hormone receptor (GHRH‐R). The present study was conducted in LOU/C/jall (LOU) rats, a strain described as a model of healthy ageing, which is characterised by a low adiposity and long life expectancy without developing severe pathologies. Effects of age and diet (chow versus self‐selection), on levels of anterior pituitary GHRH‐R mRNA transcripts, were assessed in male and female LOU rats. The effect of age on pituitary GHRH‐R functionality was examined in the anterior pituitary of both males and females fed chow diet. Moreover, serum insulin‐like growth factor‐I (IGF‐I), T4 and leptin were measured because changes in their concentration could affect GHRH‐R expression. In the pituitary of 18‐month‐old male and female LOU/C/jall rats fed standard chow, the level of 2.5‐kb GHRH‐R mRNA transcript, coding for functional GHRH‐R, was significantly decreased. In 24‐ to 34‐month‐old males and females, it progressively returned to the level of younger animals, suggesting an enrichment of the group with survivors maintaining functional GHRH‐R. In males and females repeatedly submitted to self‐selection, this phenomenon was not observed. Studies with the GHRH‐R agonist, Fluo‐GHRH, revealed that 73% of 16–18‐month‐old male and female rats studied did not show an increase of fluorescence density characteristic of receptor‐mediated internalisation upon incubation at 37 °C. In the other 27%, the increase of fluorescence was identical to that observed in pituitaries of young rats, suggesting the presence of an optimal level of functional GHRH‐R. Serum levels of leptin, free T4 and total IGF‐I decreased more drastically in ageing males and in rats fed a self‐selection diet. A positive correlation was demonstrated between leptin and IGF‐I levels in ageing males and females fed standard chow and ageing females submitted to a self‐selection regimen. In conclusion, healthy ageing in LOU rats fed chow diet appears to be associated with a maintenance of functional pituitary GHRH‐R levels found in younger rats but not necessarily with those of serum leptin, T4 and IGF‐I.
Bibliography:ark:/67375/WNG-05HLLQ70-G
ArticleID:JNE1343
istex:1D8E3ECFA2883624A224DDB1AE8FFFB5DEF22E9B
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0953-8194
1365-2826
DOI:10.1111/j.1365-2826.2005.01343.x