Adenosine deaminase (ADA) characterization in saliva and serum samples of different animal species

Background The enzymatic activity of total adenosine deaminase (tADA) and its isoenzymes ADA1 and ADA2 were studied in canine, equine, porcine and bovine serum and saliva. Erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) was used as a specific ADA1 inhibitor at different concentrations, and the distribution of the isoenzymes in serum and saliva was studied in different inflammatory situations in each species. Results Total ADA was present in serum and saliva of healthy animals of the four species. EHNA concentration of 0.47mM was needed for ADA1 inhibition in canine and porcine samples (serum and saliva) and bovine saliva, whereas for equine saliva 0.94mM was needed. ADA2 activity was not detected in bovine serum and was very low or absent in equine serum and bovine saliva. An automated procedure to measure ADA2 consisting of adding EHNA to a commercial reagent for tADA measurement provided repetitive (coefficients of variation <8.8% in serum and <10% in saliva) and accurate (linearity under dilution approaches gave R 2 >0.90) results, being equivalent to a manual incubation of the sample with EHNA at a similar concentration. Salivary tADA, as well as ADA1 and ADA2, were higher in dogs with leishmaniosis, horses with acute abdominal disease and pigs with lameness than in healthy animals. ADA showed significant correlation with serum ferritin in dogs ( r = 0.602, P < 0.01; r = 0.555, P < 0.05; and r = 0.632, P < 0.01; respectively for tADA, ADA1 and ADA2) and serum C-reactive protein in pigs ( r = 0.700, P < 0.01, for both tADA and ADA1; r = 0.770, P < 0.001, for ADA2), whereas salivary ADA2 significantly correlated with serum amyloid A in the horse ( r = 0.649, P < 0.01). In the cow, salivary tADA and ADA1 significantly increased after calving, being correlated with total white blood cell count ( r = 0.487, P < 0.05, both). Conclusions ADA activity, as well as its isoenzymes, can be measured in serum and saliva of different animal species, and the salivary levels of these analytes could potentially be inflammatory biomarkers in these species.