Kinetic regularities of NO donation by binuclear dinitrosyl iron complexes with thiolate ligands based on thiophenol derivatives in the presence of red blood cells

The kinetics of nitrogen oxide release by binuclear dinitrosyl iron complexes (B-DNICs) with thiolate ligands based on thiophenol and its several oxy, amino, and nitro derivatives was studied using a suspension of red blood cells simulating the internal medium of a blood vessel. The NO donating ability of the complexes was estimated by the kinetic parameters of first-order equation, which described the formation of intra-erythrocytic methemoglobin. Three typical kinetic profiles of NO donation were distinguished: pseudosaturation donation and donation with prolonged and explosive profiles. In the case of first-type NO donation typical of complexes with thiophenol and its nitro derivatives, the curves display a fast coming to saturation long before the complete release of all NO groups contained in the structure of the starting complex into a solution. Such a type of donation is likely due to the formation of long-lived nitrosyl intermediates in the system. The prolonged type of NO donation shown by the complex with hydroxyphenyl ligand is characterized by virtually constant rate of NO release into a solution without pronounced transition to saturation during experiment (10–12 min). In the case of explosive-type donation characteristic of the complex with aminophenyl ligands, a considerable portion of NO was fast released into a solution within 1–3 min. All complexes under study caused hemolysis of a 0.2% suspension of red blood cells. The complex with aminophenyl ligands exhibited the highest hemolytic activity.