Objective To study the outward potassium current in myocytes from septic shock rats and the effects of adrenomedullin(ADM).Methods Ventricular myocytes were isolated from adult rats 4 h after an intraperitoneal injection of lipopolysaccharide(LPS,10 mg/kg).Transient outward K~+ current(I_(to)),steady-state K+ current(I_(ss))and ATP sensitive potassium current(I_(K,ATP))were recorded using whole cell patch-clamp methods.Results LPS treatment had no effect on Ito and Iss.The I_(K,ATP) density in septic shock group[(2.66±0.56) pA/pF,n=12]was significantly higher than that in control group[(0.27±0.08) pA/pF,n=14,P＜0.01].The ADM antagonist ADM-(22-52)significantly reversed the increased I_(K,ATP)[(0.69±0.21) pA/pF,n=11,P＜0.01 vs LPS group]in shock myocytes.I_(K,ATP) density was lower in LPS plus aminoguanidine myocytes[(0.77±0.18) pA/pF,n=10,P＜0.01 vs LPS group]than that in LPS myocytes.ADM-(22-52)and 100 μmol/L aminoguanidine could completely abolish the increase in I_(K,ATP).Conclusion I_(K,ATP) was activated in myocytes from septic shock rats.Adrenomedullin along with NO precipitated activation of the I_(K,ATP) in rat ventricular myocytes during septic shock.