Comparison of sympathomimetic amines with collagen, calcium ionophor and adenosine diphosphate in their effects on thromboxane formation of human platelet rich plasma.

Platelet rich plasma (PRP) was stimulated by addition of epinephrine, norepinephrine, dopamine, dobutamine, ADP, collagen or A 23187 in various concentrations. Before, during and after aggregation the levels of thromboxane B2 (TxB2) were measured by radioimmunoassay. After addition of collagen or A 23187 a strong stimulation of thromboxane synthesis was observed, beginning with the early aggregation phase. TxB2 values after complete aggregation amounted to 110-220 ng/ml and up to 500 ng/ml, respectively. After ADP, epinephrine and norepinephrine the thromboxane formation took place mainly in the late aggregation phase and reached levels of 37-51 ng TxB2/ml PRP. Dopamine and dobutamine in concentrations up to 50 microM failed to stimulate platelet's thromboxane synthesis and induced only small changes of optical density of PRP.