Measurement of Carbonic Anhydrase I and II Isozymes in Feces as a Marker of Occult Blood in Horses with Intestinal Tract Bleeding.

The research aims to identify a simple and reliable marker for intestinal bleeding in horses. The study investigates the use of carbonic anhydrase isozymes (CA-I and CA-II), derived from red blood cells, as a potential fecal marker for this condition. The experiments showed that these isozymes increased in horses’ fecal samples displaying symptoms of gastric ulcer syndrome.

Identifying the Need

• Currently, the most definitive method for diagnosing colonic ulcers in horses is through endoscopy.
• This approach, however, poses financial and operational challenges due to the high cost of the necessary equipment and its complexity.
• As such, there is a demand for a cost-effective, reliable, and easy-to-use testing method to detect intestinal bleeding.

Carbonic Anhydrase Isozymes as a Potential Marker

• The researchers studied the use of carbonic anhydrase isozymes (CA-I and CA-II) as markers for detecting hidden or “occult” blood in the feces of horses.
• These isozymes come from erythrocytes, commonly known as red blood cells.
• The team used an enzyme-linked immunosorbent assay (ELISA) to measure these isozymes’ presence in fecal samples.

Methodology and Results

• A 2 g sample of feces was prepared using 4 ml of 0.01 M Tris-HCl at a pH level of 8.0, also containing 0.01% thimerosal.
• Initially, the study checked the fecal samples from 13 clinically normal racehorses—those with no diagnosed medical conditions—and found that CA-I and CA-II concentrations averaged 30.0 ± 10.0 and 34.0 ± 13.0 ng/ml respectively.
• In a subsequent experiment, blood was administered to 5 horses, resulting in increased concentrations of CA-I, but not CA-II in their fecal samples.
• The team then examined the fecal samples from 88 racehorses showing signs of equine gastric ulcer syndrome (EGUS) and recorded CA-I and CA-II amounts of 115.3 ± 79.0 and 41.0 ± 42.0 ng/ml, respectively.

Conclusions

• The results point towards the potential application of CA isozymes as markers for occult blood in horse feces, thereby offering a less invasive and simpler method of detecting intestinal bleeding in horses.
• Notably, the increase in CA-I concentrations following blood administration and among EGUS-affected horses suggests that this isozyme may serve as a more accurate marker compared to CA-II in these instances.