Concentrations of thromboxane metabolites in feline urine

OBJECTIVE To determine the predominant thromboxane (TX) metabolite in urine of healthy cats, evaluate whether the method of sample collection would impact concentration of that metabolite, and propose a reference interval for that metabolite in urine of healthy cats. ANIMALS 17 cats (11 purpose-bred domestic shorthair cats, 5 client-owned domestic shorthair cats, and 1 client-owned Persian cat). PROCEDURES All cats were deemed healthy on the basis of results for physical examination, a CBC, serum biochemical analysis, urinalysis, and measurement of prothrombin time and activated partial thromboplastin time. Voided and cystocentesis urine samples (or both) were collected. Aliquots of urine were stored at -80°C until analysis. Concentrations of TXB₂, 11-dehydroTXB₂, and 2,3 dinorTXB₂ were measured with commercially available ELISA kits. Urinary creatinine concentration was also measured. RESULTS 11-dehydroTXB₂ was the most abundant compound, representing (mean ± SD) 59 ± 18% of the total amount of TX detected. In all samples, the concentration of 11-dehydroTXB₂ was greater than that of 2,3 dinorTXB₂ (mean, 4.2 ± 2.7-fold as high). Mean concentration of 11-dehydroTXB₂ for the 17 cats was 0.57 ± 0.47 ng/mg of creatinine. A reference interval (based on the 5% to 95% confidence interval) of 0.10 to 2.1 ng of 11-dehydroTXB₂/mg of creatinine was proposed for healthy cats. CONCLUSIONS AND CLINICAL RELEVANCE In this study, 11-dehydroTXB₂ was the major TX metabolite in feline urine. Measurement of this metabolite may represent a noninvasive, convenient method for monitoring in vivo platelet activation in cats at risk for thromboembolism.