Studies on pulmonary secretions. 3. The nucleic acids in whole pulmonary secretions from patients with cystic fibrosis, bronchiectasis, and laryngectomy.

Abstract

The presence of deoxyribonucleic acid (DNA) in the pulmonary secretions of patients with cystic fibrosis, bronchiectasis, and laryngectomy has been confirmed by direct isolation and chemical characterization. No abnormal bases have been detected in the isolated DNA, and the base composition is closely related to that of normal human DNA. The DNA is contained within the water-insoluble fraction of the secretions. Ribonucleic acid has not been demonstrated by a variety of chemical and enzymic tests. The isolated DNA from whole secretions or the water-insoluble fraction is readily split by exogenous deoxyribonuclease (DN ase I or streptodornase). The viscosity of the secretions shows an apparent decrease concomitant with the enzymic splitting. At pH 7, exogenous DNase II shows less, but detectable, activity against the DNA of the secretions, and this activity was enhanced by adjustment of the pH to 5. Endogenous DN ase activity could not be demonstrated on incubation of fresh pulmonary secretions. The DNase activity of cystic fibrosis tissues is comparable both qualitatively and quantitatively to that of normal control tissues. The activity of the nucleases liberated into the secretions may be impaired by an unfavorable pH for the action of DNase II and the presence of a naturally occurring inhibitor for DNase I. The accumulation of DNA in pulmonary secretions is probably a result of the exudative inflammatory process outstripping the disposal mechanisms of the lung.