Different serum insulin-like growth factor-1 (IGF-1) binding characteristics accompany reduced growth associated with low thyroid hormone and/or low total IGF-1 status in young pigs
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Serum IGF-I binding patterns were determined for 3-month-old pigs exhibiting a wide range of total IGF-I and thyroid hormone (TH) concentrations. Both variables positively correlated with their growth No differences in labelled IGF-I binding patterns after molecular sieve chromatography or in ligand blots were found in pig sera with different TH levels and high IGF-I concentrations ( gt 13.1 nmol/). When serum IGF-I concentrations were low, ligand blots in the position expected for IGF binding protein-2 (IGFBP-2) were more intense and relative binding to 40 kDa serum proteins greater. Since at high TH concentrations binding to the 150 kDA fraction was unchanged, the total bound/free ratio was significantly higher than in sera from the other pigs. At low TH concentrations binding of labelled IGF-I to the 150 kDa fraction tended to decrease leading to a significantly different ratio between the two bound fractions compared with the other sera. Thus the dynamics and/or extent of IGF-I bin...ding in porcine serum may be altered in two different ways depending on TH status, possibly indicating different paths towards lower weight gain associated with separate or combined decreases in serum IGF-I and TH concentrations.
Keywords:growth / IGF-1 / thyroid hormones / pigs / IGFBP / iodine
Source:Acta Veterinaria, Beograd, 1998, 48, 1, 3-18
- Veterinary Faculty, Belgrade