Iohexol, platelet activation and thrombosis. I. Iohexol-induced platelet secretion does not affect thrombus formation in native blood

Background: The nonionic monomer iohexol triggers in vitro platelet secretion of β-thromboglobulin (β-TG). This iohexol platelet activation may promote intravascular thrombosis. We studied this relationship by employing a human model of collagen-induced platelet thrombus formation at arterial flow. The ionic dimer ioxaglate, the nonionic dimer iodixanol, and glucose were included. Methods and Results: In vitro platelet activation as measured by β-TG secretion following a 1-min incubation of native blood with 50 vol% of iohexol was significant. Glucose solutions of 300, 580 and 825 mosmol, corresponding to the osmolalities of respectively iodixanol, ioxaglate and iohexol, increased the β-TG secretion in parallel with the osmolalities. Ioxaglate and iodixanol were virtually inert. Continuous infusion of iohexol or 580 or 825 mosmol glucose (40 vol%) into flowing native blood at an arterial wall shear rate of 2600 s−1 in an ex vivo collagen-induced platelet thrombus formation device triggered pronounced secretion of β-TG. However, the platelet thrombus formation in blood mixed with iohexol was within the same range as that observed with ioxaglate or iodixanol. Increasing glucose osmolality induced increasing β-TG secretion, which paralleled gradually decreasing platelet thrombus formation. Conclusion: Iohexol and 580 or 825 mosmol glucose trigger platelet secretion of β-TG. This secretion is not associated with enhanced collagen-induced platelet thrombus formation at high arterial shear.