Serum thromboxane B2 (TXB2) Determination is Influenced by Sample Incubation Temperature in Healthy Beagle Dogs

Abstract

The measurement of serum thromboxane B 2 (TXB 2 ) production by platelets is a specific test for assessment of platelet cyclooxygenase (COX-1) activity following administration of non-steroidal anti-inflammatory drugs (NSAIDs). The aim of this study was to investigate the influence of sample incubation at 37 C for one hour on serum TXB 2 concentration in comparison with incubation at room temperature. A total of 54 blood samples for serum TXB 2 measurements were collected from six healthy beagle dogs into two separate serum tubes. While one group of tubes was incubated in a 37 C water bath, the second group of tubes was left to coagulate at room temperature, both for one hour. Serum TXB 2 concentrations were measured by ELISA. The mean concentration (± SD) of serum TXB 2 in the group of samples that were incubated at 37 C was significantly (P  0.0001) higher compared to the group of samples incubated at room temperature, 1098 ± 346 g/l and 550 ± 257 g/l, respectively.The results of the study provide the information on serum TXB 2 concentration in healthy beagle dogs and demonstrate that validated methods for assessment of COX-1 activity by measurement of serum TXB 2 should be used in order to make results more reliable and comparable between different studies. The results of this study might be of great help in planning NSAID studies in dogs by providing the information that TXB 2 generation by platelets is influenced profoundly by incubation temperature.

Selective inhibition of cyclooxygenase‐2 by enflicoxib, its enantiomers and its main metabolites in vitro in canine blood

“…The data from the assays of inhibition of COX‐1 in the absence of inhibitor showed mean basal‐stimulated TXB 2 levels that ranged from 1016.6 to 1353.5 ng/ml after curve fitting ( E 0 parameter). These values agree with those described elsewhere in dog under the same experimental conditions of incubation and serum generation (Gilmer et al, 2003 ; Jerin et al, 2009 ). Metabolite M8 and the (R)‐(+)‐Enflicoxib enantiomer did not induce a decrease of the TXB 2 levels (the data could not be fitted to any inhibitory Equation), while enflicoxib, the (S)‐(‐)‐Enflicoxib enantiomer and the pyrazol metabolite effectively inhibited COX‐1.…”

“…These values agree with those described elsewhere in dog under the same experimental conditions of incubation and serum generation (Gilmer et al, 2003;Jerin et al, 2009). Metabolite M8 and the (R)- The results of the COX-2 inhibition assay showed mean E 0 levels of PGE 2 that agreed previously published works (King et al, 2010) and ranged from 188.8 to 232.1.3 ng/ml after LPS stimulation.…”