Alterations of β-adrenoceptor responsiveness in postischemic myocardium after 72 h of reperfusion

To determine the effect of a completely developed reperfused myocardial infarction model on β-adrenoceptor responsiveness, we induced a 90-min regional ischemia followed by 72 h of reperfusion in dog hearts. Regional myocardial blood flow was determined after 60 min of ischemia using radioactive microspheres. β-adrenoceptor density was reduced in the ischemic endocardium (95±16 fmol/mg) and epicardium (160±13 fmol/mg) compared to the nonischemic region (304±21 fmol/mg). β-adrenoceptor density in the ischemic endocardium varied with the degree of collateral blood flow measured ( r 2=0.79, P