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  • Title: Impaired cytosolic calcium mobilization and aggregation in response to collagen in platelets from Japanese black cattle with Chediak-Higashi syndrome.
    Author: Shiraishi M, Ikeda M, Ogawa H, Tu CH, Ito K.
    Journal: Am J Vet Res; 1998 Jun; 59(6):744-9. PubMed ID: 9622745.
    Abstract:
    OBJECTIVE: To examine whether impaired aggregation of platelets from Japanese Black cattle with Chediak-Higashi syndrome (CHS) was attributable to mobilization of cytosolic Ca2+. ANIMALS: 4 healthy Japanese Black cattle and 3 Japanese Black cattle with CHS. PROCEDURE: Aggregation and mobilization of cytosolic Ca2+ in response to various receptor agonists was measured in platelets from healthy cattle and cattle with CHS. Involvement of endogenous ADP and arachidonic acid in collagen-induced responses was examined. Cytosolic Ca2+ concentration was measured after platelets were loaded with the Ca2+ indicator fura-PE3. Platelet aggregation was measured with an aggregometer. RESULTS: Collagen (3 to 15 micrograms/ml)-induced increases in cytosolic Ca2+ concentration and aggregation were markedly impaired for platelets from cattle with CHS, compared with values for platelets from healthy cattle. Although aggregation and the sustained phase of the cytosolic Ca2+ response to ADP were also decreased in platelets from cattle with CHS, these decreases were small, compared with those in response to collagen. A cyclooxygenase inhibitor and a phospholipase A2 inhibitor did not have any effect on peak cytosolic Ca2+ concentration or collagen-induced aggregation of platelets from healthy cattle. Responses to a P2 tau-purinoceptor antagonist suggested that decreased release of endogenous ADP was only partially involved in the impaired response to collagen among platelets from cattle with CHS. CONCLUSIONS AND CLINICAL RELEVANCE: Marked inhibition of collagen-induced Ca2+ mobilization, rather than decreased release of endogenous substances, appeared to be the major cause of impaired platelet response to collagen and the hemorrhagic tendency in cattle with CHS.
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