Fig. 1

Changes in adenosine deaminase (ADA) activity after adding increasing concentrations of erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) in the different species of this study. Serum (solid circle) and saliva (empty square) from apparently healthy dogs (a, n = 5), horses (b, n = 5), pigs (c, n = 5) and cows (d, n = 5), with increasing EHNA concentration in the reaction mixture. The changes due to the presence of EHNA at different concentrations were assessed by Friedman’s, followed by Dunn’s multiple comparison tests. Letters indicate statistically significant results with the results obtained without EHNA (a: P < 0.05; b: P < 0.01; c: P < 0.001). Greek symbols indicate statistically significant results with the 0.01 mM EHNA concentration (α: P < 0.05). The horizontal dotted line shows the lower limit of quantification according to previously reported results [22, 28]. The best EHNA concentration for achieving complete ADA1 inhibition was selected based on that concentration able to reduce ADA activity and from which no greater significant inhibition was seen