[Inhibition of platelet aggregation by dinitrosyl iron complexes with low molecular weight ligands]

The dinitrosyl iron complexes (DNIC) with thiosulphate, cysteine or phosphate were shown to inhibit in vitro (in citrate plasma) the human platelet aggregation induced by ADP, collagen or adrenaline. This effect cannot be explained by the toxic action of DNIC on the platelet membrane, since DNIC-pretreated platelets are capable of aggregating under the action of 10(-8) M/ml of phorbol ester, which is known to cause direct activation of protein kinase C. The antiaggregatory activity of DNIC exceeds that of Na-nitroprusside and seems to be due to nitric oxide capable to activate guanylate cyclase of platelets. Using the EPR method, it was shown that addition of DNIC to platelet-enriched plasma results in a rapid transfer of Fe(NO)2 groups to the coupled RS(-)-groups proteins of plasma and, apparently, of platelet membrane proteins. These protein DNIC seem to be the source of NO which inhibits human platelet aggregation.