Albuterol is a bronchodilator that primarily acts on which tissue?

• A. Bronchiolar smooth muscle
• B. Alveolar epithelium
• C. Pulmonary capillary endothelium
• D. Esophageal muscle

Answer: (A)

Bronchodilators like albuterol work by relaxing smooth muscle in the airways to open them up. Albuterol is a beta-2 adrenergic agonist, so it stimulates beta-2 receptors on the smooth muscle of the bronchioles. This activates a cascade that raises cAMP inside the muscle cells, causing relaxation and thus bronchodilation. That direct action on bronchiolar smooth muscle is what reduces airway resistance and improves airflow, especially during asthma or bronchoconstriction.

The other tissues aren’t the primary sites for this effect. Alveolar epithelium is involved in gas exchange, not regulating airway diameter. Pulmonary capillary endothelium is part of the vascular side of the lung, not the smooth muscle controlling airway caliber. Esophageal muscle has no role in the airway’s smooth-muscle tone.