INVESTIGATION OF ROLE FOR OXIDANT STRESS IN VASCULAR TOLERANCE DEVELOPMENT TO GLYCERYL TRINITRATE IN-VITRO

1 The role of reactive oxygen species (ROS) during the development of vascular cellular tolerance to glyceryl trinitrate (GTN), was studied in the rat isolated aorta. 2 Nitrate tolerance induced by a 30 min inc ubation with GTN (30 or 100 mu M) in vitro, was not affected by pretre atment with the intracellular superoxide anion scavenger, tiron (10 mM ), or the intracellular scavenger of peroxynitrite anion and hydroxyl radical, dimethylsulphoxide (DMSO, 0.2% v v(-1)). In contrast, pretrea tment with the intracellular sulphydryl donor, N-acetyl-L-cysteine (NA C, 1 mM), significantly attenuated GTN-induced tolerance. 3 Pretreatme nt with a putative inhibitor of oxidant stress-mediated, transcription factor NF-kappa B activation, pyrrolidine dithiocarbamate (PDTC, 50 m u M), an inhibitor of gene activation by NF-kappa B, dexamethasone (1 mu M) or an inhibitor of protein synthesis, cycloheximide (10 mu M), f ailed to affect tolerance development to GTN. 4 Pretreatment with DMSO (0.2% v v(-1)) or PDTC (50 mu M) depressed non-tolerant vasorelaxatio n to GTN (1 nM-1 mu M) per se. 5 Tiron (10 mM) abolished the reduction of ferricytochrome c by a superoxide anion generating system, assesse d photometrically in vitro. In contrast, DMSO (0.2% v v(-1)), NAC (1 m M) and PDTC (50 mu M) were without effect. 6 Our data suggests that ne ither oxidant stress nor nuclear activation, is important in the devel opment of cellular tolerance to GTN in rat isolated aortic smooth musc le.