Bronchoalveolar lavage fluid urea as a measure of pulmonary permeability in healthy smokers

The effects of cigarette smoking on blood to airway pulmonary permeability to the low-molecular-weight solute urea were investigated, in an attempt to evaluate its use as a dilution marker for bronchoalveolar lavage (BAL) stu dies. Five healthy normal smokers who smoked a cigarette 10 min prior to undergoi ng a 3 x 60 mL bronchoalveolar lavage (BAL), and five nonsmokers who also u nderwent BAL but without cigarette smoke exposure were studied. Five minute s before bronchoscopy, 4 MBq H-3-water and 1 MBq C-14-urea were injected in travenously and biochemical urea assays and an indirect radiotracer method were used to evaluate permeability, It was shown that the smoking group had less urea in their BAL supernatants compared to nonsmokers the results using the radiotracer method being sign ificant (p<0.005), Using both methods, it was shown that levels of urea inc reased in sequentially aspirated aliquots in both groups. The median direct ly assayed levels of urea in the smokers rose as follows: aliquot 1 0.05 mu mol.mL(-1), (range 0.03-0.14), aliquot 2 0.10 mu mol.mL(-1) (0.07-0.17), a liquot 3 0.12 mu mol.mL(-1) (0.06-0.23) (p<0.05). This led to significantly increased calculated levels of epithelial lining fluid in the sequential a liquots (p<0.05), In addition, there were large but variable amounts of lab elled water detected in both subject groups indicating a complex interactio n between the BAL procedure and the circulation. Changing urea measurements during the bronchoalveolar lavage procedure conf ound the use of the urea (epithelial Lining fluid) method for normalizing d ilution factors. The use of epithelial lining fluid determinations in smoke rs ignores the additional and probably complex permeability changes, The pr esent data suggest that acute exposure to cigarette smoke in smokers may de crease blood to airway permeability.