Therefore, because both α1- and β2-AR are highly involved in the regulation of Ca2+ flux that is essential for normal excitability and excitation-contraction coupling in cardiac myocytes and relaxation in smooth muscle [44–47], paradoxical differences in α1- and β2-AR receptor responsiveness may have critical consequences on cardiac and peripheral vascular function in CF. This evidence concerns the gene ADRB2 and cystic fibrosis.