Determination of carbonic anhydrase III isoenzyme concentration in sera of racehorses with exertional rhabdomyolysis.

The research explores the concentration of a particular isoenzyme (carbonic anhydrase III, or CA-III) in serum samples from racehorses, particularly those suffering from exertional rhabdomyolysis, a muscle disease. The study found that the concentration of this isoenzyme was significantly higher in horses with the disease, suggesting its potential as a diagnostic marker for muscle disease in horses.

Sampling and Measurement

• The researchers collected serum samples from 216 Thoroughbred horses with no clinical signs of disease. These horses were used to establish the standard range of CA-III concentrations.
• The CA-III concentrations in these samples ranged from 16.0 to 254.5 ng/ml, with an average of 56.5 ng/ml. This concentration did not vary significantly according to the age or sex of the horse.
• An enzyme immunoassay was used to determine the CA-III concentration in the serum samples. This type of assay uses antibodies to detect and measure the concentration of specific proteins, such as CA-III, in a sample.

Disease Investigation

• To investigate the relationship between CA-III and muscle disease, serum samples from 11 horses diagnosed with exertional rhabdomyolysis were analyzed. Exertional rhabdomyolysis is a condition where muscle damage occurs due to excessive exertion.
• The concentration of CA-III in these horses was, on average, 56 times higher than in the healthy Thoroughbreds, aligning with an average of 3,136 ng/ml.
• The concentration of CA-III was found to be even higher in horses with rhabdomyolysis that had been temporarily unable to stand (transiently recumbent), as compared to horses with milder disease that were simply reluctant to move.

Potential Diagnostic Use

• Finally, the researchers studied blood samples from six horses with exertional rhabdomyolysis at various stages of the disease. They found that whilst the serum activities of aldolase, creatine kinase, aspartate transaminase, and lactate dehydrogenase were high, the changes in CA-III concentration were more rapid.
• This means that changes in CA-III concentration may be detected before these other enzymes, suggesting the potential of CA-III as a diagnostic marker for muscle disease in horses.