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The aim of this study was to examine glycoconjugate secretion in human airways with and without an epithelium. Glycoconjugate release in supernatants derived from human airways in vitro was determined using an ELISA assay with an anti-human mucin monoclonal antibody (MAb 3D3). This monoclonal antibody reacted strongly with Leb antigen but also recognized in vitro Lea and Ley determinents. In 11 of the 34 different lung samples (32%) studied the glycoconjugate levels were below the threshhold of detection for this assay. The mean basal secretion of glycoconjugates in human airways in vitro was 100 ±28 μg/g tissue (Period I; n=23 different lung samples). The amount of glycoconjugate measured in the medium derived from human isolated bronchial ring preparations did not change under control conditions during the course of the experimental procedure (Period I; 128 ± 46 μg/g tissue and Period II; 159 ± 48 μg/g tissue; n=13 paired lung samples). In the supernatants of airway preparations with an intact epithelium the amount of glycoconjugates detected was 90 ± 38 μg/g tissue (Period I; n=12 different lung samples) and removal of the epithelium did not alter this basal glycoconjugate release (94 ± 60 μg/g tissue: Period I, n=8 different lung samples). The absence of the epithelial layer was confirmed by histological evaluation. Methacholine (100 μM) induced a 10- and four-fold increase in glycoconjugate release from airways with and without an epithelium, respectively. In contrast, in preparations with an epithelium, LTD4 (10 μM) and anti-IgE (dilution: 1/1000) did not cause an increase of glycoconjugate release. The methacholine difference between airways with and without an epithelium was not significantly different (P>0.10). However, a treatment with atropine (100 μM) prevented the increase of glycoconjugate release in preparations with an epithelium. These data derived from a limited number of experiments suggest that the epithelium may not regulate the basal or stimulated release of glycoconjugates from isolated human airways.

Background: Increased secretion of mucus is a hallmark of many respiratory diseases and contributes significantly to the airflow limitation experienced by many patients. While the current pharmacological approach to reducing mucus and sputum production in patients is limited, clinical studies have suggested that drugs which inhibit the cyclooxygenase and/or 5-lipoxygenase enzymatic pathways may reduce secretory activity in patients with airway disease., Aim: This study was performed to investigate the effects of indomethacin (cyclooxygenase inhibitor) and Bay x 1005 (5-lipoxygenase inhibitor) on MUC5AC release from human airways in vitro., Methods: An immunoradiometric assay was used to determine the quantities of MUC5AC present in the biological fluids derived from human airways in vitro. The measurements were made with a mixture of eight monoclonal antibodies (MAbs; PM8) of which the 21 M1 MAb recognized a recombinant M1 mucin partially encoded by the MUC5AC gene., Results: The quantities of MUC5AC detected in the biological fluids derived from human bronchial preparations were not modified after treatment with indomethacin (cyclooxygenase inhibitor) and/or an inhibitor of the 5-lipoxygenase metabolic pathway (BAY x 1005)., Conclusion: These results suggest that the cyclooxygenase and 5-lipoxygenase metabolic pathways play little or no role in the release of MUC5AC from human airways.

Background: Chronic airway diseases are often associated with marked mucus production, however, little is known about the regulation of secretory activity by locally released endogenous mediators., Aim: This investigation was performed to determine the release of MUC5AC mucin from human bronchial preparations using the purinergic agonists adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP)., Methods: Immunohistochemical and immunoradiometric assays (IRMA) were used to detect the MUC5AC mucin. Immunohistochemical analysis were performed using individual 1-13 M1 and 21 M1 MAbs recognizing a recombinant M1 mucin partially encoded by the MUC5AC gene. IRMA measurments were performed using a mixture of eight anti-M1 mucin MAbs (PM8), which included both 1-13 M1 and 21 M1 MAbs. Lysozyme and protein were also measured in the biological fluids derived from human bronchial preparations obtained from patients who had undergone surgery for lung carcinoma., Results: The anti-M1 monoclonal antibodies labelled epithelial goblet cells. After challenge of human bronchial preparations with ATP, the goblet cells exhibited less staining. In contrast, UTP did not alter the immunolabelling of goblet cells. MUC5AC mucin in the bronchial fluids derived from ATP-challenged preparations was increased while UTP had no effect on release. ATP did not alter either the quantities of lysozyme or protein detected in the biological fluids., Conclusion: These results suggest that ATP may regulate epithelial goblet cell secretion of MUC5AC mucin from human airways in vitro.