Examination of the effect of sodium nitrite on gap junction function during ischaemia and reperfusion in anaesthetized dogs.

It has previously been proved that sodium nitrite, infused prior to coronary artery occlusion or before reperfusion, results in marked antiarrhythmic effect in anaesthetized dogs. We have now examined whether this protection involves the modulation of gap junction (GJ) function by nitric oxide (NO), derived from nitrite administration under ischaemic conditions. Two groups of chloralose and urethane anaesthetized dogs, each containing 13 animals, were subjected to a 25 min period occlusion of the left anterior descending (LAD) coronary artery, followed by reperfusion. One group was infused with sodium nitrite (0.2 μmol/kg/min, i.v.), the other group with saline 10 min prior to reperfusion. The severities of arrhythmias and of ischaemia (epicardial ST-segment, total activation time), parallel with changes in myocardial tissue impedance, a measure of electrical coupling of gap junctions, were assessed during the experiments. Compared to the controls, nitrite infusion administered prior to reperfusion significantly attenuated the severity of ischaemia, the ischaemia-induced impedance changes and, consequently, the severity of arrhythmias, occurring during the 1B phase of the occlusion, and increase survival following reperfusion (0% vs. 85%). It is concluded that the marked antiarrhythmic effect of sodium nitrite is partly due, to the preservation of the electrical coupling of GJs by NO.