PT  - JOURNAL ARTICLE
AU  - Michael John Mihm
AU  - Christen Marie Coyle
AU  - Liang Jing
AU  - John Anthony Bauer
TI  - Vascular Peroxynitrite Formation during Organic Nitrate Tolerance
DP  - 1999 Oct 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 194--198
VI  - 291
IP  - 1
4099  - http://jpet.aspetjournals.org/content/291/1/194.short
4100  - http://jpet.aspetjournals.org/content/291/1/194.full
SO  - J Pharmacol Exp Ther1999 Oct 01; 291
AB  - Nitroglycerin (NTG) is an important cardiovascular agent, but tolerance during continuous administration limits its clinical utility. Increased vascular superoxide production may mediate nitrate tolerance via a reduction in nitric oxide availability. Because superoxide anion and nitric oxide react avidly to form peroxynitrite, an aggressive cellular toxicant that nitrates protein tyrosine residues, we tested the hypotheses that protein nitration, indicative of peroxynitrite formation, occurs during vascular tolerance, and that protein nitration participates in tolerance development. Preincubation of rat thoracic aorta segments with NTG (22 μM, EC95 for 30 min) caused a significant shift in NTG relaxation response (EC50; 6.7 ± 1.7 versus 0.50 ± 0.13 μM, NTG versus vehicle,p < .05). After functional evaluations, tissues were fixed in formalin for immunohistochemistry and digital image analysis. NTG-induced vascular tolerance was associated with increased immunoprevalence of 3-nitrotyrosine (3NT, stable biomarker of protein nitration; 11.41 ± 2.48 versus 0.04 ± 0.02% positive pixels, NTG versus vehicle, p < .05). Staining was observed throughout vascular smooth muscle layers. Addition of 500 μM free tyrosine to the preincubation medium did not alter tolerance development (NTG EC50 6.5 ± 3.0 μM) but abolished 3NT immunoprevalence (0.16 ± 0.10%). No significant relationship between NTG potency and 3NT immunoprevalence was observed. These data support the hypothesis that protein nitration occurs during nitrate vascular tolerance, however, it apparently does not mediate this phenomenon. The American Society for Pharmacology and Experimental Therapeutics