Accordingly, we quantified levels of the two main β-AR isoforms, β1-AR and β2-AR, as well as levels of the stimulatory and inhibitory G proteins Gαs and Gαi, respectively, in isolated hearts exposed either to baseline perfusion (B), baseline perfusion plus ischemia (I), or baseline perfusion plus ischemia plus reperfusion (IR). Here, ADRB1 is linked to ischemia.