Modification of platelet aggregation and thromboxane synthesis by intravascular contrast media

Radiographic contrast media (RCM) decreased significantly platelet aggregation in human platelet-rich plasma (PRP) after addition of arachidonic acid (AA) or adenosine diphosphate (ADP). Unlike hypertonic saline, diatrizoate, ioxaglate, and iopamidol (40 and 160 mM) inhibited AA-induced aggregation. One hundred sixty mM ioxaglate inhibited slightly the concomitant formation of immunoreactive thromboxane B2 (TXB2). The ionic RCM ioxaglate (40 and 160 mM) and diatrizoate (160 mM), but not the nonionic iopamidol, decreased the ADP-induced aggregation more than hypertonic saline. When PRP was incubated with different RCM without any aggregating agents or with ADP, the formation of TXB2 was negligible. Results of this study show that inhibition of AA- and ADP-induced platelet aggregation by RCM is partly due to hypertonicity and partly related to the chemical structure of the RCM molecule. The inhibition of AA-induced aggregation is not caused by the lack of formation of aggregatory TXA2.