Role of endogenous reactive oxygen derived species and cyclooxygenase mediators in 5-hydroxytryptamine-induced contractions in rat aorta: relationship to nitric oxide.
Endogenous reactive oxygen species (superoxide anion, hydroxyl radical and hydrogen peroxide), endothelium-derived nitric oxide and cyclooxygenase mediators are involved in the regulation of vascular smooth muscle tone. An imbalance of these mediators can have profound implications in various cardiovascular disorders. Involvement of endogenous reactive oxygen species, endothelium-derived nitric oxide (NO) and cyclooxygenase mediators in 5-hydroxytryptamine- (5-HT-) induced contractions of endothelium intact rat aortic rings have been investigated in the present study. The contribution of each of the endogenous reactive oxygen species in mediating 5-HT-induced contractions was studied by pretreating the rings with their respective scavengers. Pretreatment of the rings with superoxide dismutase (superoxide radical scavenger), catalase (H (2)O (2)inactivator), mannitol (extracellular OH. scavenger), or thiourea (intracellular OH. radical scavenger) significantly depressed the 5-HT-induced contractions in the aortic rings. The responses to 5-HT in the presence of SOD or catalase were augmented byL -NAME pretreatment. Though aminotriazole partially inhibited the catalase activity, it inhibited 5-HT-induced contractions significantly. The results obtained thus suggest that endogenous generation of ROS (O(2).(-), H (2)O (2)and OH.) modulates 5-HT-induced rat aortic ring contractions. In addition, H (2)O (2)generated in the endothelium seems to regulate the vascular response and also act as a mediator to release other vasoactive substances. Basal production of NO by the endothelium seems to affect the vascular response due to its interaction with ROS mediators.
Division of Pharmacology, Central Drug Research Institute, Lucknow 226 001, India. madhudikshit@yahoo.com
P
P
Srivastava
M
M
Rajanikanth
S A V
SA
Raghavan
M
M
Dikshit
D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000502:physiology; D002374:Catalase / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052250:Nitric Oxide Synthase Type III; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology*; D011453:Prostaglandins / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000494:pharmacology
D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D011453:Prostaglandins; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D012701:Serotonin; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D002374:Catalase; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D011451:Prostaglandin-Endoperoxide Synthases; D013482:Superoxide Dismutase; D019331:NG-Nitroarginine Methyl Ester; D000640:Amitrole