ACE2 and infection: Hence, as the consequence of infection of various cells including pulmonary cells of lungs, myocytes of heart, proximal tubular cells of kidney, and other ACE2-expressing cells (which mainly express CAs) with SARS-CoV-2 and reducing the ability of CO2 exhalation, the concentration of blood CO2 is elevated so even the lungs alveoli became unable in O2-CO2 exchange with pulmonary artery and vein through the CA enzymatic reaction [69].