This work was performed at the College of Veterinary Medicine, Mississippi State University
Platelet Cyclooxygenase Expression in Normal Dogs
Article first published online: 30 AUG 2011
Copyright © 2011 by the American College of Veterinary Internal Medicine
Journal of Veterinary Internal Medicine
Volume 25, Issue 5, pages 1106–1112, September/October 2011
How to Cite
Thomason, J., Lunsford, K., Mullins, K., Stokes, J., Pinchuk, L., Wills, R., Mclaughlin, R., Langston, C., Pruett, S. and Mackin, A. (2011), Platelet Cyclooxygenase Expression in Normal Dogs. Journal of Veterinary Internal Medicine, 25: 1106–1112. doi: 10.1111/j.1939-1676.2011.00781.x
funded by the Mississippi State University College of Veterinary Medicine Internal Competitive Research Grant and Dr. Hugh G. Ward Endowment.
Abstract previously presented in part at the 2010 ACVIM Forum, Anaheim, CA, June 2010.
The authors thank Mandy Wallace for her assistance.
- Issue published online: 20 SEP 2011
- Article first published online: 30 AUG 2011
- Manuscript Accepted: 5 JUL 2011
- Manuscript Revised: 30 MAY 2011
- Manuscript Received: 31 JAN 2011
Human platelets express both cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Variation in COX-2 expression could be a mechanism for variable response to aspirin.
The hypotheses were that circulating canine platelets express COX-1 and COX-2, and that aspirin alters COX expression. The objective was to identify changes in platelet COX expression and in platelet function caused by aspirin administration to dogs.
Eight female, intact hounds.
A single population, repeated measures design was used to evaluate platelet COX-1 and COX-2 expression by flow cytometry before and after aspirin (10 mg/kg Q12h for 10 days). Platelet function was analyzed via PFA-100® (collagen/epinephrine), and urine 11-dehydro-thromboxane B2 (11-dTXB2) was measured and normalized to urinary creatinine. Differences in COX expression, PFA-100® closure times, and urine 11-dTXB2 : creatinine ratio were analyzed before and after aspirin administration.
Both COX-1 and COX-2 were expressed in canine platelets. COX-1 mean fluorescent intensity (MFI) increased in all dogs, by 250% (range 63–476%), while COX-2 expression did not change significantly (P = 0.124) after aspirin exposure, with large interindividual variation. PFA-100® closure times were prolonged and urine 11-dTXB2 concentration decreased in all dogs after aspirin administration.
Conclusions and Clinical Importance:
Canine platelets express both COX isoforms. After aspirin exposure, COX-1 expression increased despite impairment of platelet function, while COX-2 expression varied markedly among dogs. Variability in platelet COX-2 expression should be explored as a potential mechanism for, or marker of, variable aspirin responsiveness.