Bronchoalveolar lavage is used to obtain cells and proteins from the lower respiratory tract for diagnosis and research. Uncertainity exists about which site in the lung is sampled by the lavage fluid and what effect different lavage volumes have on recovery of the constituents of lavage fluid. Dilution of alveolar lining fluid by lavage fluid is variable and results are usually expressed as protein ratios to surmount this problem. We have compared cell profiles and the concentrations of two proteinase inhibitors--the low molecular weight bronchial protease inhibitor antileucoprotease and alpha 1 proteinase inhibitor, together with alpha 1 proteinase inhibitor function and its relationship to the cell profile in sequential bronchoalveolar lavage fluid samples from patients undergoing bronchoscopy. There was no difference in total or differential cell counts or albumin or alpha 1 proteinase inhibitor concentrations between the first and second halves of the lavage. Both the concentration of antileucoprotease and the ratio of antileucoprotease to albumin were, however, lower in the second half of the lavage (2p less than 0.01 and 2p less than 0.05 respectively). There was no difference in the function of alpha 1 proteinase inhibitor (assessed by inhibition of porcine pancreatic elastase--PPE) between aliquots (0.28 mole PPE inhibited/mol alpha 1 proteinase inhibitor; range 0-1.19 for the first half and 0.37 mol PPE inhibited/mol alpha 1 proteinase inhibitor; range 0.10-0.80 for the second half). About 60-70% of alpha 1 proteinase inhibitor in each half of the lavage fluid was inactive as an inhibitor. The function of alpha 1 proteinase inhibitor did not differ between bronchitic smokers and ex-smokers. Alpha 1 proteinase inhibitor function was not related to the number of total white cells, macrophages, or neutrophils in the lavage fluid. Contamination of lavage by red blood cells was found to alter the concentration of alpha 1 proteinase inhibitor but not its function when aliquots with and without erythrocytes were compared. These results show that the only difference between the two halves of these lavage samples is in the amount of antileucoprotease present, suggesting that more proximal secretions are being harvested early in the lavage procedure. Much of the alpha 1 proteinase inhibitor present in the samples is functionally inactive, but this is not clearly related to any particular cell type or to smoking habits, and does not differ between different stages of the lavage procedure. Much of the alpha1 proteinase inhibitor present in the samples is functionally inactive, but this is not clearly related to any particular cell type or to smoking habits, and does not differ between different stages of the lavage procedure. Finally, the presence of erythrocytes probably does affect alpha(1) proteinase inhibitor concentration and such samples should be excluded from analysis.
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