PT - JOURNAL ARTICLE AU - S. Dikalov AU - B. Fink AU - M. Skatchkov AU - D. Stalleicken AU - E. Bassenge TI - Formation of Reactive Oxygen Species by Pentaerithrityltetranitrate and Glyceryl Trinitrate <em>In Vitro</em> and Development of Nitrate Tolerance DP - 1998 Aug 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 938--944 VI - 286 IP - 2 4099 - http://jpet.aspetjournals.org/content/286/2/938.short 4100 - http://jpet.aspetjournals.org/content/286/2/938.full SO - J Pharmacol Exp Ther1998 Aug 01; 286 AB - Anti-ischemic therapy with organic nitrates is complicated by tolerance. Induction of tolerance is incompletely understood and likely multifactorial. Recently, increased production of reactive oxygen species (ROS) has been investigated, but it has not been clear if this is a direct consequence of the organic nitrate on the vessel or anin vivo adaptation to the drugs. To examine the possibility that nitrates could directly stimulate vascular ROS production, we compared the development of nitrate tolerance with the formation of ROS induced by pentaerithrityltetranitrate (PETN) or nitroglycerin (GTN) in vitro in porcine smooth muscle cells, endothelial cells, washed ex vivo platelets and whole blood. By examining cGMP formation, it was found that 24-hr treatment with GTN but not PETN induced significant nitrate tolerance, which was prevented by parallel treatment with Vit C. Incubation of vascular cells acutely with 0.5 mM GTN doubled the rate of ROS generation, whereas PETN had no such effect. The rate of ROS (peroxynitrite and O2—˙) formation detected by specific spin traps in tolerant smooth muscle cells, treated for 24 hr with 0.01 mM GTN, was substantially higher (30.5 nM/min) than in control cells acutely treated with 0.5 mM GTN (25 nM/min). In contrast to PETN, GTN induces nitrate tolerance and also increases the formation of ROS both in vascular cells and in whole blood. ROS formation is minimally stimulated by PETN comparable to data obtained in Vit C-suppressed GTN tolerance. ROS formation induced by organic nitrates seems to be a key factor in the development of nitrate tolerance. The American Society for Pharmacology and Experimental Therapeutics