Acute phase response in horses: changes in plasma cation concentrations after localised tissue injury.

The research investigated how localized tissue injuries in horses trigger acute phase reaction, focusing on changes in plasma concentrations of certain metal ions. It was found that inflammation can alter plasma copper, iron, and zinc levels, possibly providing insight into diagnosing and monitoring inflammatory conditions in horses.

Objective and Methodology

• The aim of the study was to understand how an acute phase response in horses affects the plasma concentrations of certain cations (copper, iron, and zinc) following localized tissue injury.
• Four horses were treated with Freund’s adjuvant, a substance commonly used to provoke an immune response, intramuscularly to induce a local inflammatory reaction.

Findings and Interpretations

• After the administration of the adjuvant, changes in the plasma concentrations of copper, iron, and zinc were observed.
• Plasma copper concentration, plasma ceruloplasmin copper concentration ( ceruloplasmin is a copper-carrying protein in the blood) and ceruloplasmin oxidase activity increased steadily, peaking 24 days post-administration. The plasma copper concentration rose by 90 per cent compared to the baseline concentration.
• The constant ratio of plasma ceruloplasmin copper to total plasma copper suggested that both components serve as acute-phase reactants in horses, indicating they increase in response to inflammation.
• Conversely, plasma zinc and iron concentrations were reduced to 59 per cent and 30 per cent of their initial levels respectively, possibly reflecting an organism’s attempt to limit access to these elements for potential pathogens.
• The severity of the inflammation seemed to influence the plasma concentrations of the metals, suggesting that these changes could serve as a biomarker for inflammation.

Implications and Limitations

• Weak correlations between plasma fibrinogen concentration (fibrinogen is a protein involved in blood clotting and often rises in inflammation) and plasma copper and zinc concentrations suggested that a single measurement of plasma copper concentration might not be useful for diagnosing non-specific inflammatory disorders in horses.
• Notwithstanding, the results suggest that serial measurements of plasma copper concentrations could be helpful in monitoring the resolution of inflammatory disorders in horses.