title: Protective effect of histidine on hydroxyl radical generation induced by potassium-depolarization in rat myocardium.
abstract: We investigated the efficacy of histidine on potassium-depolarization induced hydroxyl radical (*OH) generation in the extracellular fluid of rat myocardium by a flexibly mounted microdialysis technique (O system). After the rat was anesthetized, a microdialysis probe was implanted in the left ventricular myocardium, and then sodium salicylate in Ringer's solution (0.5 nmol/microl per minute) was infused to detect the generation of *OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (DHBA). Infusion of KCl (70 mM) clearly produced an increase in *OH formation. However, when KCl in the presence of a high concentration of histidine (25 mM) was infused through the microdialysis probe, KCl failed to increase the 2,3-DHBA formation. To examine the effect of histidine on ischemia-reperfusion of the myocardium, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, a marked elevation of the levels of 2,3-DHBA was observed in the heart dialysate. However, when corresponding experiments were performed with histidine (25 mM)-pretreated animals, histidine prevented the ischemia-reperfusion induced *OH formation trapped as 2,3-DHBA. These results indicate that histidine may protect against K+-depolarization-evoked *OH generation in rat myocardium.
authors.affiliation: Department of Pharmacology, Oita Medical University, Hasama-machi, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Obata
authors.forename: M
authors.initials: M
authors.lastname: Aomine
authors.forename: Y
authors.initials: Y
authors.lastname: Yamanaka
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology*; D062385:Hydroxybenzoates / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012980:Sodium Salicylate / Q000494:pharmacology
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D062385:Hydroxybenzoates; D017665:Hydroxyl Radical; D006639:Histidine; D011189:Potassium Chloride; C009135:2,3-dihydroxybenzoic acid; D011188:Potassium; D012980:Sodium Salicylate