Abnormal platelet function in Chediak-Higashi syndrome.

Platelets in an infant with Chediak-Higashi (C-H) syndrome without bleeding manifestations and not in the accelerated phase showed abnormal function consistent with storage pool disorder as shown by abnormal aggregation, decreased storage capacity and release of [14C]5-HT, low endogenous 5-HT, reduced ATP and ADP with an increased ATP/ADP ratio, increased specific radioactivity of ADP after [14C]adenine labelling, decreased release of adenine nucleotides after stimulation, impaired secretion of acid hydrolases despite normal stores, and decreased calcium content. Incorporation of [14C]adenine into metabolic pool adenine nucleotides was normal. Nucleotide conversion to hypoxanthine in stimulated platelets was mildly impaired. Platelet cyclic-AMP (c-AMP) was initially elevated, but even when c-AMP returned to normal levels after ascorbate treatment, platelet function was not improved. Elevated intracellular c-AMP was not solely responsible for the abnormal platelet function.