Composition and control of secretions from tracheal bronchial submucosal glands

Abstract

TRACHEAL bronchial submucosal (TBS) glands are thought to supply a significant fraction of respiratory tract fluid (RTF)1, which is critically important in cleaning the airways of the lung. In the cleaning process, cilia in the tracheal bronchial tree continuously sweep the RTF, with debris, out of the lung. But abnormalities in the physicochemical properties of the RTF may impair this clearance, resulting in fluid stagnation, infection and obstruction of the airways. Unfortunately, because of the small size and inaccessibility of TBS glands and the difficulty in collecting their uncontaminated secretions, little is known about their physiology. We have developed methods for collecting and analysing secretions from single TBS glands of the cat in vitro, and we describe here the composition and control of the fluid secreted by these glands. We have found that the composition of the secreted fluids is very similar to that of the extracellular fluid and that secretion flow rates are influenced predominantly by α-adrenergic and cholinergic agonists. In view of the well known exocrinopathy in the lethal genetic disease cystic fibrosis (CF)2, we believe these findings to have implications for pathological changes in the airways in this disease.