Alterations of somatotropic function in prion disease in sheep.
This study aimed at investigating the possible linkage between natural scrapie and alterations of the somatotropic axis. Scrapie-affected ewes exhibited 2-fold higher mean GH concentrations during both autumn and spring. GH pulse frequencies were higher in scrapie-affected ewes than in control animals (mean+/-S.E.M. number of pulses/24 h: 10.4+/-0.9 and 7.6+/-0.9 for scrapie-affected and control ewes respectively) suggesting the involvement of central mechanisms. GH secretion induced by administration of an alpha(2)-adrenergic agonist, which acts centrally to stimulate GH secretion, was similar between healthy and scrapie-affected ewes (ratios of the area under the curve (AUC) of GH concentration after to the GH AUC before the agonist administration were 3.6+/-1.6 and 4.9+/-1.0 for scrapie-affected and control ewes respectively). Finally, humoral markers and parameters of the metabolic status were determined to test the hypothesis that scrapie-associated alterations of GH secretion could be related to disruption of metabolic homeostasis. Glucose, insulin and urea plasma concentrations were higher in scrapie-affected than in healthy ewes. Neither leptin nor IGF-I levels were affected by scrapie. Total thyroxine (T4) was decreased in scrapie-affected ewes but free T4 and total and free triiodothyronine were not modified. In conclusion, our results showed the existence in scrapie-affected ewes of endocrine and metabolic alterations typical of acute illness proceeding, at least in part, from central mechanisms.
Viguié
C
C
UMR 181, Experimental Pathophysiology and Toxicology, INRA National Veterinary School of Toulouse, 31076 Toulouse cedex 3, France. c.viguie@envt.fr
Chilliard
Y
Y
Gayrard
V
V
Picard-Hagen
N
N
Monget
P
P
Dutour
A
A
Toutain
P-L
PL
D000208:Acute Disease; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D007328:Insulin / Q000097:blood; D008297:Male; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012608:Scrapie / Q000097:blood / Q000503:physiopathology*; D012621:Seasons; D012636:Secretory Rate / Q000187:drug effects; D012756:Sheep; D013974:Thyroxine / Q000097:blood; D014508:Urea / Q000097:blood
D000316:Adrenergic alpha-Agonists; D001786:Blood Glucose; D007328:Insulin; D014508:Urea; D013006:Growth Hormone; D013974:Thyroxine