Introduction Pyometra is relatively common in intact bitches

Introduction Pyometra is relatively common in intact bitches and its diagnosis is aided by ultrasonography (Bigliardi et al., 2004), along with measurement of acute phase proteins and leucocyte (white blood cell, WBC) counts; assessment of these parameters during recovery may be helpful for monitoring systemic inflammation and for detecting early complications (Dąbrowski et al., 2009, Jitpean et al., 2014). Saliva can be used for evaluation of markers of inflammation and stress, and can be collected relatively non-invasively and with minimal stress in veterinary species, including dogs, for the evaluation of markers of inflammation and stress (Vincent and Michell, 1992, Parra et al., 2005). Adenosine deaminase (ADA; Enzyme Commission number 3.5.4.4) is an enzyme that catalyses the irreversible conversion of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. This enzyme has been proposed in human beings as a biomarker of inflammation (Mishra et al., 1994). ADA activity is increased in saliva in human beings with squamous cell carcinoma of the tongue (Rai et al., 2011). In experimental infection of dogs with Ehrlichia canis, serum ADA activity decreased at 12 days, then increased at 30days after infection (Da Silva et al., 2013). ADA activity is decreased in bitches with mammary tumours compared to unaffected dogs (Machado et al., 2015) and in dogs with leishmaniasis compared to uninfected dogs (Tonin et al., 2016). Therefore, the role of ADA as a marker of inflammation in dogs is still to be fully elucidated. Dogs may perceive different degrees of stress when they face new situations, such as a visit to a veterinary clinic or being hospitalised. This induced stress reaction can involve the sympathetic-adrenomedullary (SAM) system and the hypothalamic-pituitary-adrenal (HPA) axis. Salivary chromogranin A and α-amylase (Enzyme Commission number 3.2.1.1) are considered to be markers of activation of the SAM system in the dog, whereas calcium sensing receptor concentrations increase in dogs after activation of the HPA (Contreras-Aguilar et al., 2017a, Srithunyarat et al., 2017). Serum cortisol concentrations are increased in bitches with pyometra and decrease after treatment (Reinoldes, 2010).
Materials and methods
Results
Discussion Salivary ADA activity was significantly higher in dogs with pyometra than in healthy dogs and was significantly correlated with the serum inflammatory biomarkers CRP, Hp and WBC count. Since previous studies have correlated ASA grade with outcome (Sigrist et al., 2008, Goggs et al., 2015), the relationship between ASA and salivary parameters was studied in order to evaluate their possible prognostic usefulness. ADA activity was correlated with ASA grade, indicating that it could be of value as a prognostic factor, although this should be tested in a larger population of dogs and with a range of post-operative outcomes. Salivary ADA activity was not correlated with serum ADA activity. Furthermore, serum ADA activity was not correlated with any inflammatory marker, so the role of serum ADA as inflammatory biomarker in dogs requires further study, since it could be unaffected, as in our study, or could increase (Da Silva et al., 2013) or decrease (Machado et al., 2015, Tonin et al., 2016), depending on the specific disease. One dog in the healthy group had a very high ADA activity in saliva for an unknown reason; this activity remained high when values were normalised by the protein content. The possible different sources of this enzymatic activity in saliva should be studied further to improve our understanding of its role. In human beings, increases in salivary ADA activity have been associated with oral diseases, such as squamous cell carcinoma of the tongue, increasing as the stage of the disease increases (Rai et al., 2011). Accelerated purine metabolism and the salvage pathway activity of purine nucleotides in cancerous human oral tissues has been proposed as a mechanism, suggesting that ADA could have a role in the progression and invasion of cancer (Rai et al., 2011).