Contractile agonists increase Ca2+ sensitivity of contraction Relaxation mediated by an increase in intracellular cAMP or cGMP is often associated with a decrease in Ca2+ sensitivity. Two ways to modulate Ca2+ sensitivity:    alter balance of rMLC kinase and MLCP at constant Ca2+    rMLC phosphorylation-independent regulatory mechanisms such as    caldesmon or calponin or HSP20, which may disrupt phosphorylated    myosin-actin cross bridges.