DIMERIC AND MONOMERIC FORMS OF DINITROSYL IRON COMPLEXES WITH THIOL-CONTAINING LIGANDS - PHYSICOCHEMICAL PROPERTIES AND VASODILATOR ACTIVITY

When studying the vasodilator activity of dinitrosyl iron complexes (D NIC) with thiol-containing ligands as NO donors, it should be taken in to consideration that these complexes depending on the content of thio ls in the environment can occur in either form that differ by their EP R, gamma-resonance and optical characteristics and also by their vasod ilator effect on isolated blood vessels. The more stable diamagnetic f orm appears at the ratio Fe2+:RS(-)=1:2. It reversibly dissociates to the monomeric paramagnetic form [(RS(-))(2)Fe+(NO+)(2)] on increasing the thiol content to the level 20 times and more exceeding the quantit y of iron. It is suggested that stabilization of the dimeric form is p rovided by formation of RS(-)-NO+ bonds between monomeric components o f the dimer. This process is favored by a corresponding orientation of the monomers relative to each other. A high stability of the DNIC dim eric form correlates with more prolonged vasodilator effect of this co mplex as an NO source. Replacement of cysteine by reduced glutathione in dimeric and monomeric forms of DNIC increases both stability of the complexes and the duration of theit vasodilator effect.