Automated Spectrophotometric Assays for the Measurement of Ammonia and Bicarbonate in Saliva of Horses: Analytical Validation and Changes in Equine Gastric Ulcer Syndrome (EGUS)

Abstract

Ammonia (NH3) and bicarbonate (HCO3) have been related to gastric ulcers in humans. Ammonia is considered a possible cause of gastric ulcers, whereas bicarbonate has a protective function. The presence of ulcers in the stomach of horses is defined as Equine Gastric Ulcer Syndrome (EGUS), which is a frequent disease in this species, and it has been associated with changes in saliva composition, such as in analytes related to inflammation, immune system and oxidative stress. The objectives of this study were (1) to perform an analytical validation of two automated spectrophotometric assays, one for ammonia and one for bicarbonate, in the horses’ saliva and (2) to evaluate their possible variations with EGUS. Analytical validation of the automated assays for ammonia and bicarbonate in the saliva of horses showed that both assays were precise and accurate. In addition, significantly higher values of ammonia and lower values of bicarbonate were found in the saliva of horses with EGUS compared to healthy horses. It can be concluded that ammonia and bicarbonate can be measured in the saliva of horses and that ammonia increases and bicarbonate decreases in this sample type could be related to the presence of EGUS in this species.

Cystatin C, Ammonia, and Bicarbonate Measurements in the Saliva of Pigs: Analytical Validation and Changes in S. suis Infection

“…Based on this data, the assays could be used for the measurements of Cystatin C, ammonia, and bicarbonate in the saliva of pigs. To our knowledge, this is the first report of a specific assay for the measurement of cystatin C in the saliva of any animal species, and in the case of ammonia and bicarbonate, the validation results of this study were similar to those obtained in an analytical validation of these methods made in horse saliva [14]. In the case of ammonia and bicarbonate, the assays validated are spectrophotometric and, therefore, potentially could also be used in other animal species; however, for cystatin C, since it is an immunoturbidimetric assay that uses antibodies, a previous validation in the species to be used should be performed.…”

“…The evaluation of the stability after storage indicated that the three analytes are stable for short-term storage at −80 °C, at −20 °C and even at −4 °C in the case of cystatin C. Artifactual changes in ammonia and bicarbonate have been described in horse saliva and human saliva at room temperature [ 14 , 26 ]. In accordance with this data, storage at −80 °C would be recommended for these analytes.…”

“…The increase in ammonia in sepsis can lead to encephalopathy, and it is recommended that serum ammonia levels be closely monitored in patients with sepsis [ 13 ]. To our knowledge, ammonia has not been evaluated in the saliva of sepsis or the saliva of pigs, but this is an analyte that can be measured in the saliva of humans and horses [ 14 ].…”

“…Bicarbonate has been measured in the saliva of pigs, giving similar values to that in humans [ 18 ]. Recently, changes in concentrations of ammonia and bicarbonate were detected in horses with gastric ulcers [ 14 ]. However, to the author`s knowledge, there is no analytical validation data of the measurement of bicarbonate in the saliva of pigs.…”

Measurement of Trace Elements (Zinc, Copper, Magnesium, and Iron) in the Saliva of Horses: Validation Data and Changes in Equine Gastric Ulcer Syndrome (EGUS)

“…Saliva is used as a sample for the measurement of biomarkers that can be related to stress, the immune system, inflammation, redox status, and the general metabolism of individuals. In horses, it can be obtained by easy collection procedures without producing stress or pain, and in cases of EGUS, changes have been described in various biomarkers, showing even differences depending on the type of EGUS [ 21 , 22 ]. However, to the authors’ knowledge, there are no reports about trace elements in the saliva of horses.…”