Human respiratory mucus.

Respiratory mucous glycoproteins may serve a number of protective functions for the airways; however, excessive secretions contribute to the morbidity of a variety of diseases including asthma, chronic bronchitis, and cystic fibrosis. Respiratory secretions are a mixture of cells, fluid, transudated and locally produced proteins, and mucous glycoproteins. The mucous glycoproteins give these secretions their characteristic viscosity and elasticity. While the physiologic control of mucous glycoprotein secretion is not completely understood, cholinergic, alpha-adrenergic, and beta-adrenergic stimuli may all contribute. Respiratory mucus hypersecretion seen in immediate hypersensitivity or inflammatory states may be due to reflex hypersecretion, to a variety of mediators (including histamine and cyclooxygenase or lipoxygenase pathway metabolites of arachidonic acid), or to substances released from phagocytic cells (such as macrophages, monocytes, or neutrophils). The limited number of specific approaches currently available for treating respiratory mucus hypersecretion include therapy of any underlying or intercurrent disease, improving clearance of secretions, and reducing mucus secretion with the use of glucocorticosteroids or anticholinergic drugs.