Characterization of certain inflammatory variables in the peripheral blood of clinically healthy dogs.

Many laboratory techniques have been developed to study and quantify the inflammatory response, including the release of acid hydrolase enzymes, leukotriene B(4) (LTB(4)) production, reactive oxygen species (ROS) production and complement conversion studies. Although extensively studied in human health and disease, the relevance of such tests in the dog is largely unknown. After isolation of the peripheral blood mononuclear cell (PBMC) and polymorphonuclear cell (PMN) fractions from the peripheral blood of 38 clinically healthy dogs, values for ROS production were similar for both cell fractions when measured by luminol-enhanced chemiluminescence (17,853+/-9,695 U/10(6) cells versus 19,138+/-14,569 U/10(6) cells for the PBMC (n=38) and PMN (n=18) fractions, respectively). However, the mean time taken to reach maximum chemiluminescence was noticeably shorter in the PBMC fraction (5.1+/-3.3 versus 10.7+/-2.5 min for PBMCs (n=36) and PMNs (n=18), respectively). Intracellular concentrations of beta-glucuronidase, beta-galactosidase and N-acetyl-beta-glucosaminidase were assayed by spectrofluorometry. Mean values for all three enzymes were higher in PBMCs (n=31-35) than in PMNs (n=10-14). Both cell fractions released 20% of the intracellular enzyme concentration when stimulated with opsonized zymosan. Following incubation with A23187 (1 microM), mean LTB(4) production was higher in PBMCs (4.45+/-2.92 ng/10(6) cells; n=27) than in PMNs (0.96+/-2.22 ng/10(6) cells; n=13) using a validated high performance liquid chromatography (HPLC) assay. Immunoprecipitation studies revealed that the mean percentage conversion of C3 to C3b following stimulation with opsonized zymosan was 57.3+/-13.4% (n=36). The results provide normal values for clinically healthy dogs that may subsequently be used in future studies investigating dogs with various inflammatory disorders.

Increased leukotriene B(4) production, complement C3 conversion and acid hydrolase enzyme concentrations in different leucocyte sub-populations of dogs with atopic dermatitis.

Various markers of the inflammatory response were measured in peripheral blood mononuclear cells (PBMCs) and polymorphonuclear neutrophils (PMNs) from 31 dogs with atopic dermatitis (AD). The variables assayed included chemiluminescence, acid hydrolase enzyme concentrations, leukotriene B(4) (LTB(4)) production and complement C3 conversion. The results were compared to those derived from a population of clinically healthy dogs. Dogs with AD exhibited a significant increase in median LTB(4) production in PMNs compared to controls (0.94 versus 0.00 ng/10(6) cells; P<0.01). Significant increases in the median concentrations of intracellular beta-galactosidase (PBMC fraction - 0.42 versus 0.25 mU/10(6) cells; P<0.05) (PMN fraction - 0.47 versus 0.12 mU/10(6) cells; P<0.01) and beta-glucuronidase (PBMC fraction - 0.52 versus 0.27 mU/10(6) cells; P<0.05) were also evident in the AD group. Although median maximum chemiluminescence values for both leucocyte sub-populations were higher in controls, the differences recorded were not significant (P>0.05). However, the median time taken to reach maximum chemiluminescence was significantly shorter in the PMN fraction of dogs with AD (7.00 versus 10.00 min; P<0.01). Atopic dogs had a significant increase in the median percentage conversion of complement C3 to C3b (66.0 versus 57.3%; P<0.01). The results of this study indicate a priming of the inflammatory response in dogs with AD. The role of LTB(4) in the pathogenesis of canine AD and the potential efficacy of leukotriene antagonists in the treatment of this disorder warrant further investigation.