کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2394068 | 1101372 | 2007 | 24 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Insulin-like growth factor type-1 receptor down-regulation associated with dwarfism in Holstein calves Insulin-like growth factor type-1 receptor down-regulation associated with dwarfism in Holstein calves](/preview/png/2394068.png)
Perturbations in endocrine functions can impact normal growth. Endocrine traits were studied in three dwarf calves exhibiting retarded but proportionate growth and four phenotypically normal half-siblings, sired by the same bull, and four unrelated control calves. Plasma 3,5,3′-triiodothyronine and thyroxine concentrations in dwarfs and half-siblings were in the physiological range and responded normally to injected thyroid-releasing hormone. Plasma glucagon concentrations were different (dwarfs, controls > half-siblings; P < 0.05). Plasma growth hormone (GH), insulin-like growth factor-1 (IGF-1) and insulin concentrations in the three groups during an 8-h period were similar, but integrated GH concentrations (areas under concentration curves) were different (dwarfs > controls, P < 0.02; half-siblings > controls, P = 0.08). Responses of GH to xylazine and to a GH-releasing-factor analogue were similar in dwarfs and half-siblings. Relative gene expression of IGF-1, IGF-2, GH receptor (GHR), insulin receptor, IGF-1 type-1 and -2 receptors (IGF-1R, IGF-2R), and IGF binding proteins were measured in liver and anconeus muscle. GHR mRNA levels were different in liver (dwarfs < controls, P < 0.002; dwarfs < half-siblings, P = 0.06; half-siblings < controls, P = 0.08) but not in muscle. IGF-1R mRNA abundance in liver in half-siblings and controls was 2.4- and 2.5-fold higher (P = 0.003 and P = 0.001, respectively) and in muscle tissue was 2.3- and 1.8-fold higher (P = 0.01 and P = 0.08, respectively) than in dwarfs. Hepatic IGF-1R protein levels (Western blots) in muscle were 2.5-fold higher (P < 0.05) and in liver and muscle (quantitative immunohistochemistry) were higher (P < 0.02 and P < 0.07, respectively) in half-siblings than in dwarfs. The reduced presence of IGF-1R may have been the underlying cause of dwarfism in studied calves.
Journal: Domestic Animal Endocrinology - Volume 33, Issue 3, October 2007, Pages 245–268