Thrombelastographic Demonstration of Nitrite Inhibition of Platelet Function

Abstract 5148

We have recently shown that nitrite ions in blood will inhibit platelet aggregation and activation as measured by aggregometry and flow cytometric analysis of P-selectin under partially deoxygenated conditions. We now show that these phenomena can be measured by thrombelastographic analysis, an alternative method which supplies additional parameters of clotting, using whole blood from healthy donors. Nitric oxide (NO) can be generated by endogenous nitric oxide synthase (NOS) as well as by a serial reduction pathway in which nitrate and nitrite are converted to NO via several enzymatic and nonenzymatic mechanisms. We have previously shown that nitrite anions at 0. 1μM inhibit platelet activation and aggregation in the presence of red blood cells through their reduction to NO and this effect was enhanced by deoxygenation. In the present study, we examined the influence of nitrite on the clotting properties of blood to investigate how nitrite may affect overall clotting processes by modulating platelet function. We measured major clotting parameters such as reaction time (R, minute of initial fibrin formation), angle (velocity of clot growth), and maximum amplitude (MA, clot strength) using thrombelastograph hemostasis analyzer (TEG5000^®) in whole blood diluted with plasma to yield 20% Hct. Both the NO donor (DEANONOate) and nitrite showed inhibitory effects on clotting parameters resulting in delayed R, decreased angle, and reduced MA in a dose dependent manner. However, the sources of NO did not change any TEG parameters in plasma. These results suggest that this new clinical method may be used to follow NO inhibition of platelet-induced blood clotting and that the physiological effect of factors which determine NO bioavailability, such as endogenous levels of blood and tissue nitrite, could be used as biomarkers for predicting hemostatic potential.