ATTENUATION BY DEXAMETHASONE OF ENDOTOXIN PROTECTION AGAINST ISCHEMIA-INDUCED VENTRICULAR ARRHYTHMIAS

Ventricular arrhythmias from a 30 min occlusion of the left coronary a rtery were assessed in Langendorff perfused isolated hearts removed fr om rats administered either saline, or endotoxin derived from Escheric hia coil (2.5 mg kg(-1) i.p.) given either 2, 4, 8, 24 or 48 h previou sly. Arrhythmia severity was markedly reduced in those hearts removed from rats administered endotoxin with a maximum protection at 8h; ther e was a marked reduction in the incidence of ventricular fibrillation (from 54% to 4%) and in the number of ventricular premature beats duri ng the occlusion period (e.g. from 1165 +/- 144 to 37 +/- 19; P < 0.01 ). Dexamethasone (3 mg kg(-1), given 1 h prior to endotoxin or saline) markedly attenuated the protection afforded by endotoxin.