ADRB3 and heart disorder: Of the 3 βARs subtypes (β1AR, β2AR, and β3AR)expressed in the heart, β1ARs are the most abundant (~75–80%)with some expression of β2ARs (~15–20%) and minimal expressionof β3AR.45,46 Subsequent discoveries led to additionalunderstanding of their roles in the pathophysiology of heart disease, such as theobservations of beta-receptor downregulation45,47 and alteredexpression of GRKs48 in heartfailure.