Effect of Beta₂ Receptor Activation on Smooth Muscle

The beta₂ receptor associated with smooth muscle also utilizes the cAMP signaling system.  However, the results of receptor mediated increases in cAMP levels in smooth muscle are different are different than those occurring in cardiac muscle.  Therefore, the consequences of PKA phosphorylation of key structures in smooth muscle signaling in beta₂receptor systems.

Structures Phosphorylated in Smooth Muscle

1.) sarcolemma - Decrease Ca²⁺ influx

2.) sarcoplasmic reticulum - Enhance Ca²⁺ uptake

3) decrease actin-myosin interactions-muscle relaxation

The net result of these activities is to inhibit calcium pathways in smooth muscle leading to relaxation.