Angiotensin-I converting enzyme (ACE) is a key regulator of blood pressure, electrolytes and fluid homeostasis through conversion of angiotensin I into angiotensin II. Recently, a genetic polymorphism of the ACE gene, which accounts for 47% of the variation of ACE activity in blood, has been advocated as a biomarker of athletic aptitude. Different methods of analysis and determination of ACE activity in plasma have been used in human and equine research without a consensus of a "gold standard" method. Different methods have often been used interchangeably or cited as being comparable in the existing literature; however, the actual agreement between assays has not been investigated. Therefore, in this study, we evaluated the level of agreement between three different assays using equine plasma obtained from 29 horses. Two spectrophotometric assays using Furylacryloyl-phenylalanyl-glycyl-glycine as substrate and one fluorimetric assay utilizing o-aminobenzoic acid-FRK-(Dnp)P-OH were employed. The results revealed that the measurements from the different assays were not in agreement, indicating that the methods should not be used interchangeably for measurement of equine ACE activity. Rather, a single method of analysis should be adopted to achieve comparable results and critical appraisal of the literature is needed when attempting to compare results obtained from different assays.
Animals ; Enzyme Assays/*methods ; Female ; Fluorometry/*methods ; Horses/blood/genetics/*metabolism ; Male ; Oligopeptides/pharmacology ; Peptidyl-Dipeptidase A/blood/genetics/*metabolism ; Polymorphism, Genetic ; Reference Values ; Spectrophotometry/*methods

This study aimed to measure the levels of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 1 (IL-1), interleukin 6 (IL-6), and nitrite/nitrate (NOx) in serum of dogs experimentally infected with Rangelia vitalii. Twelve female mongrel dogs were divided into 2 groups; group A (uninfected controls) composed by healthy dogs (n=5) and group B consisting of dogs inoculated with R. vitalii (n=7). Animals were monitored by blood smear examinations, which showed intraerythrocytic forms of the parasite on day 5 post-infection (PI). Blood samples were collected through the jugular vein on days 0, 10, and 20 PI to determine the serum levels of IFN-gamma, TNF-alpha, IL-1, IL-6, and NOx. Cytokines were assessed by ELISA quantitative sandwich technique, and NOx was measured by the modified Griess method. Cytokine levels (IFN-gamma, TNF-alpha, IL-1, and IL-6) were increased (P<0.01) in serum of infected animals. Serum levels of NOx were also increased on days 10 PI (P<0.01) and 20 PI (P<0.05) in infected animals. Therefore, the infection with R. vitalii causes an increase in proinflammatory cytokines and nitric oxide content. These alterations may be associated with host immune protection against the parasite.
Animals ; Chemistry Techniques, Analytical ; Cytokines/*blood ; Disease Models, Animal ; Dogs ; Enzyme-Linked Immunosorbent Assay ; Female ; Nitric Oxide/*blood ; Piroplasmida/*immunology ; Protozoan Infections/*immunology/parasitology/pathology ; Serum/chemistry