thromboxane-b2 and Chediak-Higashi-Syndrome

The beige (bgJ/bgJ) mouse is a well-described murine model of Chediak-Higashi syndrome. Platelet function was examined in normal and beige mice to better characterize the defective aggregation response in platelets from mice with Chediak-Higashi syndrome. Platelet aggregation after collagen, thrombin, and phorbol-12-myristate 13-acetate stimulation was significantly (P less than 0.025) decreased in platelets from beige mice, relative to platelets from normal mice. Compared with beige and normal mice, those heterozygous for the bg trait had intermediate responses to collagen and thrombin, but not phorbol-12-myristate 13-acetate. The defect(s) in aggregation of platelets from beige mice was associated with a dense granule storage pool deficiency and decreased stores of serotonin and adenine nucleotides in platelets. Mice heterozygous for the bg trait had normal platelet serotonin and adenine nucleotide concentrations. Platelets from beige mice were approximately 10 times more sensitive to prostacyclin inhibition of collagen-induced aggregation than were platelets from control mice. However, a significant difference in platelet cyclic AMP concentration was not apparent between beige and normal mice after prostacyclin stimulation. Platelet endoperoxide synthesis measured by quantification of thromboxane B2, was normal in beige mice. Protein phosphorylation patterns in mouse platelets were similar to those seen in human platelets. Thrombin and collagen-induced [32P] phosphorylation of 40- and 20-kD proteins in platelets from normal and beige mice was similar. Results indicate that the biochemical defect(s) in platelet function in beige mice is partially attributable to storage pool deficiency and does not result in an absolute defect in phosphorylation of 40- and 20-kD proteins.

Topics: Animals; Blood Platelets; Blood Proteins; Chediak-Higashi Syndrome; Cyclic AMP; Disease Models, Animal; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Nucleotides; Phosphorylation; Platelet Aggregation; Platelet Storage Pool Deficiency; Serotonin; Thromboxane B2

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.

Topics: Adenine Nucleotides; Adenosine Diphosphate; Adenosine Triphosphate; Animals; Bleeding Time; Blood Coagulation Tests; Blood Platelets; Cats; Chediak-Higashi Syndrome; Chromatography, Gel; Female; Hemostasis; Hydrolases; Male; Malondialdehyde; Platelet Aggregation; Serotonin; Thromboxane B2

Topics: Adenosine Diphosphate; Animals; Arachidonic Acids; Blood Platelets; Cats; Chediak-Higashi Syndrome; Indomethacin; Platelet Aggregation; Serotonin; Thromboxane A2; Thromboxane B2; Thromboxanes