ADRB1 and heart valve disorder: Downregulation of β1-AR has been shown to occur in patients withleft heart valvular disease as well as chronic mitral regurgitation [166, 176].Depressions in myocardial β1-AR density, adenylyl cyclase activity,and response to isoproterenol were observed after inducing volume overload [177].A reduction in the adenylyl cyclase response to norepinephrine has been reporteddue to volume overload [167].