Enhanced platelet reactivity in heartworm-infected dogs

SUMMARY Platelet number, mean platelet volume, and platelet function were evaluated in 34 clinically normal dogs and 28 heartworm-infected (hwi) dogs. Mean platelet numbers for dogs of the hwi group was not significantly lower than those for dogs of the control group (214,000 vs 254,000 cells/μl); however, 6 (21%) hwi dogs had platelet numbers < 150,000/μl, compared with only 2 (6%) heartworm-negative dogs. The mean platelet volume was not significantly different (7.8 vs 7.7 fl) between the 2 groups of dogs. Mean platelet aggregation responses to intermediate and low concentrations of collagen (3.0 and 1.5 μg) and to high, intermediate, and low concentrations of adp (25, 10, and 5 μM) were greater in dogs of the hwi group. Mean platelet 14C-serotonin release was also greater in hwi dogs in response to high concentration of adp (25 μM) and to intermediate concentration of collagen (3.0 μg).