Pacing‐induced delayed protection against arrhythmias is attenuated by aminoguanidine, an inhibitor of nitric oxide synthase

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Abstract
Cardiac pacing, in anaesthetized dogs, protects against ischaemia and reperfusion‐induced ventricular arrhythmias when this is initiated 24 h after the pacing stimulus. Now we have examined whether this delayed cardioprotection afforded by cardiac pacing is mediated through nitric oxide. Twenty‐two dogs were paced (4×5 min periods at 220 beats min−1) by way of the right ventricle, 24 h prior to a 25 min period of coronary artery occlusion. Nine of these dogs were given the inhibitor of induced nitric oxide synthase, aminoguanidine (50 mg kg−1 i.v.), 0.5 h prior to coronary artery occlusion. Sham‐operated non‐paced dogs with and without aminoguanidine treatment served as controls. Pacing markedly (PP−1. These results suggest that nitric oxide, probably derived from induced nitric oxide synthase, contributes significantly to the delayed cardioprotection afforded by cardiac pacing. British Journal of Pharmacology (1999) 127, 1545–1550; doi:10.1038/sj.bjp.0702695