Measurement of Anions in Dog Tear Fluid Using Ion Chromatography

Anions in tears may be related to the pathogenesis of ocular surface diseases. A comprehensive method that can detect small quantities of anions in human tears has been developed. However, the differences in individual anion concentrations between tears and plasma remain unclear. This study investigated anion concentrations in dog tears.

To compare anion concentrations between tear and plasma samples in canines, 12 eyes of six healthy purpose-bred research Beagles (unneutered males, 3 years old) were investigated. Additionally, the tears of canines with various diseases were examined.

Anion concentrations were assessed using a commercially available ion chromatography system. For this, at least 10 μL of tears were collected in a glass capillary tube and diluted with 300 μL of distilled water; plasma was obtained by centrifuging collected blood samples, which were then diluted 100-fold before chromatography.

Anion concentrations differed significantly between the tears and plasma of Beagles. The average concentrations (mg/L) of anions in tears of Beagles were as follows: Cl^-, 5374.06 ± 157.06; Br^-, 27.84 ± 1.43; NO₃ ^-, 0.70 ± 0.65; HPO₄ ^2-, 77.54 ± 14.36; and SO₄ ^2-, 16.41 ± 8.17. In plasma, the values were as follows: Cl^-, 4603.81 ± 542.52; Br^-, 18.34 ± 2.78; NO₃ ^-, 1.31 ± 0.87; HPO₄ ^2-, 83.63 ± 21.04; and SO₄ ^2-, 105.14 ± 21.86. No statistically significant differences in anion concentrations were observed between tears from diseased and non-diseased eyes of canines.

Herein, we observed that certain anions, such as Br^- and Cl^-, were consistently elevated in tear fluid than in the plasma.