Equine neutrophil myeloperoxidase in plasma: design of a radio-immunoassay and first results in septic pathologies.

This research outlines the development of a novel blood test for monitoring systemic inflammation in horses. The test, based on a radioimmunoassay (RIA) technique, measures the levels of the enzyme myeloperoxidase (MPO) produced by neutrophils, a type of white blood cell. The study finds the test to be effective, suggesting its potential usefulness for diagnosing and monitoring illnesses such as intestinal obstructions in horses.

Design of a Radioimmunoassay for Equine Neutrophil Myeloperoxidase

• The researchers developed a radioimmunoassay (RIA) to measure the levels of the enzyme myeloperoxidase (MPO), a product of equine neutrophils. The neutrophils are a type of white blood cell that is often activated during inflammation or infection.
• The MPO was labeled with a radioactive iodine isotope (125I) using a process called self-labeling. The labeled MPO served to identify the presence and concentration of MPO in the blood.
• The radioimmunoassay was conducted by incubating diluted antiserum, labeled MPO, and either a reference solution or an unknown sample. After incubation, the antigen-antibody complexes were isolated using double antibody precipitation.

Testing and Results of the Radioimmunoassay

• The sensitivity of the assay was found to be 2 ng/ml, meaning this is the smallest concentration of MPO that can be detected with this technique.
• The procedure demonstrated both precision and accuracy – the intra-assay and inter-assay coefficients of variation were 6% and 8% respectively for MPO concentrations ranging from 2 ng/ml to 60 ng/ml.
• The researchers found that using ethylenediaminetetraacetic acid (EDTA) as the anticoagulant for blood collection provided the most stable values for plasma MPO.

Implications of Increased Myeloperoxidase Levels

• In samples from healthy horses, the average plasma MPO level was 69.5 ± 19.4 ng/ml.
• Stressors like transport and anesthesia did not significantly alter the mean plasma MPO value.
• Horses undergoing surgery for conditions without systemic impact showed no significant rise in plasma MPO.
• In contrast, horses suffering from obstructive intestinal pathologies showed persistently high MPO concentrations, up to 740 ng/ml, suggesting a systemic neutrophil activation.

The Clinical Potential of the Radioimmunoassay

• This radioimmunoassay offers a new way to monitor systemic inflammation in horses by measuring the levels of MPO in the bloodstream.
• The persistently high plasma MPO levels in horses suffering from obstructed intestines implies this technique could be used for diagnostic and monitoring purposes in such conditions.