Benzodifuroxan as an NO-dependent activator of soluble guanylate cyclase and a novel highly effective inhibitor of platelet aggregation

The ability of benzodifuroxan (BDF) to activate human platelet guanylate cy clase was investigated. The maximal stimulatory effect (1160 +/- 86%) was o bserved at 0.01 mM concentration. Sodium nitroprusside produced the same st imulatory effect (1220 +/- 100%) but at a higher concentration (0.1 mM). 1- H-[1,2,4,]-Oxadiazolo[4,3-alpha]quinoxalin-1-one-(ODQ), an inhibitor of NO- dependent guanylate cyclase activation, attenuated the stimulatory effect o f BDF (0.01 mM) by 75% and that of sodium nitroprusside (0.1 mM) by 80%. In creasing dithiothreitol concentration in the sample from 2.10(-6) to 2.10(- 4) M increased the stimulatory effect of BDF 2.7-fold. The possible involve ment of sulfhydryl groups of low-molecular-weight thiols and guanylate cycl ase in thiol-dependent activation of the enzyme is discussed. We have also found that BDF is a highly effective inhibitor of ADP-induced human platele t aggregation with (IC50 of 5.10(-8) M). The effect of sodium nitroprusside was much weaker (IC50 5.10(-5) M).