Introduction: Monochloramine (NH2Cl) is a reactive oxidant produced by the reaction of ammonia (NH3, generated by H. Pylori) with hypochlorous acid (HOCl, released by activated neutrophils). Targets of NH2Cl include thiol (S-H) groups on intracellular proteins such as metallothioneins. Oxidation of thiols releases Zn2+, an intracellular signal that prevents apoptosis by inhibiting conversion of procaspase-3 to caspase-3. Here we tested the hypothesis that NH2Cl activates anti-apoptotic pathways.Methods: Gastric glands were isolated from New Zealand White rabbits. To evaluate effects on [Zn2+]i, glands were loaded with the Zn2+-sensitive reporter, fluozin-3. Spontaneous caspase-3 activation was monitored by colorimetric assay, in response to Ringer's solutions containing NH2Cl: a) alone; b) in the presence of 1mM dithiotreitol (DTT), which blocks thiol oxidation; or c) in the presence of 20μM TPEN, which chelates Zn2+.Results: Acute (30 min) exposure of glands to Ca 2 2+-free Ringer's containing NH2Cl (100mM) elicited a 7.8 +/- 0.9-fold increase in fluozin-3 intensity, corresponding to an increase from 0.1nM to 8nM Zn2+ (n = 5, p < 0.001). Prolonged exposure to NH2Cl (50μM, 100μM, 200μM) elicited concentration-dependent decreases in caspase-3 activation, which were at least partially reversed by TPEN and fully reversed by DTT (Table). Cell viability, as assessed by trypan blue exclusion, was > 95% at 50μM and 100μM, but was significantly impaired (~50%) at the highest concentration (200μM). TableEffects of monochloramine (NH 2 Cl) on caspase-3 activationCondition0 NH2Cl50 μM NH2Cl100 μM NH2Cl200 μM NH2ClControl100 +/- 065.2 +/- 10.0147.8 +/- 11.319.7 +/- 3.720 uM TPEN116.8 +/- 7.4103.3 +/- 6.275.8 +/- 9.736.7 +/- 10.91 mM DTT105.8 +/- 5.9110.8 +/- 4.5108.5 +/- 5.6104 +/- 6.6Results reported relative to glands (75ug protein) incubated under control conditions: means +/- SE.*p < 0.01 compared to glands not exposed to NH2Cl. p < 0.05 compared to NH2Cl control.Conclusions: Exposure to NH2Cl is not necessarily toxic to gastric glands at concentrations expected in H. pylori-infested mucosa. Paradoxically, NH2Cl may serve as a H. pylori-generated signal that releases Zn2+ and is anti-apoptotic in gastric mucosa.