Erythromycin inhibits Cl secretion

We read with interest the report of erythromycin reducing chloride secretion in canine tracheal epithelium (1]. However, we would like to caution against extrapolating from dog to man. Canine trachea is virtually unique in its ion transport properties predominantly secreting chloride, a process which is stimulated by endogenous prostaglandin synthesis. The shortcircuit current of human airways principally relates to absorption of sodium and chloride secretion represents only a small component of this current [2]. Furthermore, it is presently unknown whether endogenous prostaglandins have any role in influencing these processes. Thus, similar studies in a sodium absorbing epithelium will be needed to assess the likelihood of the hypothesis that erythromycin alters ion and hence water transport in man. Finally, at present there is no direct evidence that we know of which demonstrates that altering airway ion transport affects the depth of the sol phase of airway surface fluid and the rheological properties of mucus to alter mucociliary clearance. Studies with amiloride [3, 4 J are suggestive that there may be such effects, but these tenets have yet to be rigorously explored. E.W.F.W. AI.ton, Lecturer in Thoracic Medicine, D.M. Geddes, Consultant Thoracic Physician, Ion Transport Laboratory National Heart and Lung Institute Manresa Road London SW3 6LR