Temperature dependence of thromboxane A2production induced by exogenous arachidonic acid and vWF. A stirred suspension of human platelets (500 μL at 50,000 cells/μL) was stimulated with either 20 μmol/L arachidonic acid (A) or a combination of 1 mg/mL ristocetin and 5 μg/mL multimeric human vWF (B) at 20°C, 25°C, 30°C, or 37°C (as indicated). Platelet thromboxane A2 production was assessed by enzyme immunoassay of its stable breakdown product, thromboxane B2. Control samples were incubated with dimethylsulfoxide (vehicle for arachidonic acid) or 1 mg/mL ristocetin alone; thromboxane A2 production in the control (typically, 0.4 ng in both cases) was subtracted from that in the corresponding experimental sample. Data are presented as a Tukey box plot: the central line in the box shows the median value for the agonist-induced increment in thromboxane A2 production from seven studies, the lower and upper limits of the box designate the quartiles, and the error bars extending below and above the box represent the 10th and 90th percentiles, respectively. Statistical analysis was based on Friedman’s test with a nonparametric Student-Newman-Keuls posthoc test; significant differences (P < .01) from measurements at the higher temperatures are designated: †compared with 37°C, and ‡compared with 30°C.
