Evaluation of the platelet storage pool deficiency in the feline counterpart of the Chediak-Higashi syndrome.

Cats with the Chediak-Higashi (CH) syndrome have abnormal hemostasis with prolonged bleeding times and normal coagulation times. Platelet aggregation induced by serotonin, ADP, and collagen was impaired. Platelets from normal and CH cats were incubated with 14C-adenine and then gel-filtered. Gel-filtered platelets (GFP) from CH cats contained 63% of the ATP, 38% of the ADP, 100% of the Ca2+, and 75% of the Mg25 of normal platelets. Serotonin could not be detected in CH platelets. Acid hydrolase and total platelet protein of CH platelets was similar to normal platelets. Gel-filtered platelets were treated with thrombin to induce maximal secretion. Secretion of ATP, Ca2+, and Mg2+ was 1.9%, 12.4%, and 16% respectively of normal platelets. ADP secretion by CH platelets was not detectable. The ATP/ADP ratio in the 14C-labeled metabolic pool of normal platelets was similar to that of total measured nucleotide pool of CH platelets. These findings suggest that in feline CH platelets, as in platelets from CH mink and cattle, there is storage pool deficiency that is virtually complete, and the virtual absence of ADP and 5HT may in part account for the abnormal hemostasis. Aggregation of platelets from CH cats was impaired, but these platelets did aggregate to arachidonate, serotonin-induced biphasic aggregation, and the aggregation response to ADP and collagen varied according to the amount of serotonin-induced TxB2 formed. These findings support a major role for arachidonate in platelet activation.