Platelet Activation and Clopidogrel Effects on ADP-Induced Platelet Activation in Cats with or without the A31P Mutation in MYBPC3.
BACKGROUND
Clopidogrel is commonly prescribed to cats with perceived increased risk of thromboembolic events, but little information exists regarding its antiplatelet effects.


OBJECTIVE
To determine effects of clopidogrel on platelet responsiveness in cats with or without the A31P mutation in the MYBPC3 gene. A secondary aim was to characterize variability in feline platelet responses to clopidogrel.


METHODS
Fourteen healthy cats from a Maine Coon/outbred mixed Domestic cat colony: 8 cats homozygous for A31P mutation in the MYPBC3 gene and 6 wild-type cats without the A31P mutation.


METHODS
Ex vivo study. All cats received clopidogrel (18.75 mg PO q24h) for 14 days. Before and after clopidogrel treatment, adenosine diphosphate (ADP)-induced P-selectin expression was evaluated. ADP- and thrombin-induced platelet aggregation was measured by optical aggregometry (OA). Platelet pVASP and ADP receptor response index (ARRI) were measured by Western blot analysis.


RESULTS
Platelet activation from cats with the A31P mutation was significantly (P = .0095) increased [35.55% (18.58-48.55) to 58.90% (24.85-69.90)], in response to ADP. Clopidogrel treatment attenuated ADP-induced P-selectin expression and platelet aggregation. ADP- and PGE1-treated platelets had a similar level of pVASP as PGE1-treated platelets after clopidogrel treatment. Clopidogrel administration resulted in significantly lower ARRI [24.13% (12.46-35.50) to 11.30% (-7.383 to 23.27)] (P = .017). Two of 13 cats were nonresponders based on OA and flow cytometry.


CONCLUSIONS
Clopidogrel is effective at attenuating platelet activation and aggregation in some cats. Cats with A31P mutation had increased platelet activation relative to the variable response seen in wild-type cats.
Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA. rhli@ucdavis.edu.
R H L
RH
Li
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA.
J A
JA
Stern
Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA.
V
V
Ho
Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA.
F
F
Tablin
Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ.
S P
SP
Harris
D000244:Adenosine Diphosphate / Q000633:toxicity*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002371:Cat Diseases / Q000139:chemically induced; D002415:Cats / Q000235:genetics* / Q000502:physiology; D000077144:Clopidogrel; D005786:Gene Expression Regulation / Q000502:physiology; D020022:Genetic Predisposition to Disease; D005838:Genotype; D009154:Mutation; D015539:Platelet Activation / Q000235:genetics / Q000502:physiology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D013927:Thrombosis / Q000139:chemically induced / Q000662:veterinary*; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000099163:Myosin Binding Protein C
D000244:Adenosine Diphosphate; D002352:Carrier Proteins; D000077144:Clopidogrel; D010975:Platelet Aggregation Inhibitors; D013988:Ticlopidine; D000099163:Myosin Binding Protein C
Cat; Hypertrophic cardiomyopathy; Platelet hyper-reactivity; Thromboembolism