Insulin-like growth factor binding proteins of equine serum.

The research focuses on discovering and analysing proteins in horse serum that bind insulin-like growth factor (IGF). Distinctly identified was a 96 kDa protein specific to horse serum not found in the serum of other animals like goats, cows, sheep, deer, and donkeys.

Identification of Insulin-like Growth Factor Binding Proteins

• In the initial stage of the research, the scientists used ligand blotting analysis. This technique allows them to identify specific proteins that bind to IGF-I, which was radiolabeled for clear detection.
• A 96 kDa protein capable of binding IGF-I was discovered in horse serum. In contrast, this protein was absent in the serum of goats, cows, sheep, deer, and donkeys.

Comparison with Other Animal Species

• Different animal species’ serum displayed five labeled bands ranging from 24 to 41 kDa. However, these bands were weakly present in horse serum.
• This demonstrates the distinct binding protein profile of horse serum compared to other animals, highlighting a unique factor contributing to IGF-I binding.

Size Exclusion Chromatography and Binding Potential

• The researchers used size exclusion chromatography of horse serum, which was pre-incubated with radiolabeled IGF-I. This process helped determine the size of the binding proteins present.
• The results illustrated a decreased binding in the 130-kDa peak in horse serum compared to goat plasma, reaffirming the existence of the unique 96-kDa protein.
• Subsequent ligand blotting analysis further confirmed the presence of this 96-kDa protein in the 130-kDa peak.

Specificity and Species-unique Nature

• The 96-kDa protein from horse serum was found to specifically bind IGF-I and IGF-II, demonstrating its purpose in the IGF pathway.
• Uniquely, this 96-kDa protein appears to be exclusive to horse serum, which is a potentially significant finding as the nature and function of this protein remain yet unknown.