Hydroxyl radical: A possible mediator of nitroglycerin-induced vascular relaxation

Lalita A. Bharadwaj; Kailash Prasad

doi:10.1007/s00547-003-0984-4

International Journal of Angiology, Table of Contents

Int J Angiol 2003; 12(2): 90-95
DOI: 10.1007/s00547-003-0984-4

Original Articles

Hydroxyl radical: A possible mediator of nitroglycerin-induced vascular relaxation

Lalita A. Bharadwaj¹ ² , Kailash Prasad³

¹Institute of Agricultural, Rural and Environmental Health, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
²Toxicology Group, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
³Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Abstract

PDF Download

Abstract

The endothelium-derived relaxing factor, nitric oxide (NO·), is involved in acetylcholine (Ach) and nitroglycerin (NTG)-induced relaxation of vascular smooth muscle. It is known that NO· interacts with the superoxide anion (O₂·⁻) at physiological pH and this interaction leads to the generation of hydroxyl radicals (·OH). Hydroxyl radicals are known to induce dilation and act as mediators in acetylcholine (Ach)-induced relaxation of rabbit aortic smooth muscle. Thus, it was hypothesized that ·OH may be involved in NTG-induced relaxation. To test this hypothesis we investigated the effect of NTG on norepinephrine (NE)-precontracted isolated rabbit aortic rings in the absence and/or presence of O₂·⁻ [superoxide dismutase (SOD)] and ·OH scavengers [dimethylthiourea (DMTU) or mannitol]. Superoxide dismutase, DMTU, and mannitol markedly reduced NTG-induced relaxation of isolated rabbit aortic rings. Superoxide dismutase produced a 32% reduction in NTG-induced vasodilation. Pretreatment with DMTU and/or mannitol reduced NTG-induced relaxation by 56% and 49%, respectively. These results suggest that ·OH may be a mediator involved in NTG-induced vascular relaxation of rabbit aorta.

PDF (141 kb)