Platelet aggregation studies in canine cyclic hematopoiesis

Investigation of platelet function in dogs with cyclic hematopoiesis (OH) revealed a platelet aggregation disorder. Collagen-induced aggregation of CH dog platelets was significantly below normal, although normal aggregation in response to ADP was observed. The failure to aggregate in response to collagen was not influenced by platelet size. Aggregation was particularly low on days 2, 3, 4 and 14 of the 14-day neutrophil cycle which is typical of CH dogs. The lack of response to collagen suggests a defect in the arachidonic acid pathway of platelet metabolism since platelet-generated thromboxane B2 was significantly (~70%) below control levels. Platelets from dogs heterozygous for CH demonstrated moderately depressed responses to collagen which were intermediate between the values found for CH dog platelets and normal, mixed breed dog platelets. Not only does this work indicate a platelet defect in CH dogs, but this phenomenon may be useful as a genetic marker in identification of dogs heterozygous for the CH gene.