| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
|---|
| Research Abstract |
The purpose of this study was to establish the dynamics of nitrotyrosine (NO_2-Tyr> formation and decay during the rise of N0_2-Tyr in rat brain subjected to 2-hour focal ischemia-reperfusion, and to evaluate the role of INOS and nNOS in the rise. We first determined the half life of N0_2-Tyr in rat brain at 24 hours after the start of reperfusion by blocking NO_2-Tyr formation with N0-monomethyl-L-arginine and following the decay of N0_2-Tyr by means of a hydrolysis/HPLC procedure. The values obtained were 2.16 and. 2.25 horn-s in pen-infarct and core-of-infarct regions, respectively. Using the same hydrolysis/HPLC procedure, we measured N0_2-Tyr levels from 2-hour occlusion up to 72 hours after the start of reperfusion, in the presence and absence of aminoguanidine (intraperitoneally 100 mg/kg twice a day). In the absence of aminoguamdine, N0_2-Tyr levels in the peri-infarct and core-of-infarct regions reached 0.95*0.34% and 0.52*0 34% respectively, at 1 hour after the start of reperfusion. The elevated levels persisted until 48 hours, then declined. The pen-infarct region showed the highest N0_2-Tyr level, followed by the core of infarct, then the caudoputamen. Aminoguanidine significantly reduced N0_2-Tyr formation (up to 90% inhibition) during 24-48 hours. Further, using the same hydrolysisfHPLC procedure, we measured N0_2-Tyr levels in 19 male CS7BIack/6J mice with 2-hour occlusion following 0.5-hour reperfusion, in the presence and absence of 7-nitro indazole (100 mg/kg, given intrapenitoneally 15 minutes before occlusion). 7-intro indazole significantly reduced N02-Tyr formation (0.10A 0.07%), compared to that in vehicle-treated. group (0.18A 0.05%). We therefore conclude that nNOS and iNOS are predominantly responsible for N0_2-Tyr formation in the early phase and the late phase of reperfusion, respectively. These results have important implications for the therapeutic time window and choice of NOS inhibitors in patients with cerebral infarction.
|
