Abstract:

Nitric oxide is involved in ischemia/reperfusion brain injury. Ischemic brain in jury and ischemia/reperfusion brain injury always associate with thrombogenesis and thrombolysis. Considering the specific ability scavenging free radicals of n itronyl nitroxides and the thrombolytic activity of the oligopeptides (ARPAK, GR PAK and QRPAK), [1-(1',3'-dioxyl-4',4',5',5'-tetra-methyldihydroimidazol-2-yl)phenyl-4-yl]oxyacetic acid (1) was introduced into their N-terminal via six reactions in 27% tota l yield. The ESR measurement demonstrates that the conjugates N-[1-(1',3'-dioxyl-4',4',5',5'-tetramethyldihydroimidazol-2-yl)-phenyl-4-yl]oxya cetyl-ARPAK (2a),-GRPAK (2b) and-QRPAK (2c) are stable NO free radicals and ha ve substantially same spectroscopy as that of 1. The free radical scavenging tests in vitro, euglobulin lys is tests in vitro and the thrombolysis tests in vivo indicated that couplling 1 and P6A or its analogues re sulted in the combination of free radical scavenging and thrombolysis actions. F or instance as H₂ O₂ scavenger the EC₅₀ of 2a-c and 1 is 28.1, 25.4, 24.1 and 30.2 μmol/L, respectively. As·OH scavenger the EC₅₀ of 2a-c and 1 is 98.1, 95.4, 94.2 and 100.0 μmol/L. As NO scavenger the EC₅₀ of 2a-c and 1 is 89.1, 9 2.3, 91.8 and 91.2 μmol/L. Comparing to 1 the free radical scavenging activities are increased. After adm inistration of 10.0 μmol/L of 2a-c,1, UK and NS the reduced thrombus mass is (19.91± 3.59)mg,(19.70± 3.76)mg,(28.85± 3.80)mg,(15.89 ± 2.53)mg,(25.40± 2.50)mg and (15.11± 3.70)mg, respectively. After administration of 10.0 μmo l/L of A RPAK, GRPAK and QRPAK the reduced thrombus mass is (18.54± 3.28)mg,(21.17± 3.06)mg and (25.82± 2.15)mg respectively. All of the mentione d data indicated that the nitronyl nitroxide modified peptide 6A and analogues po ses both of free radicals scavenging activity and thrombolysis activity.