Ciliated respiratory epithelial surface changes after formaldehyde exposure

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Abstract
The investigation sought to identify alterations of specific ciliated epithelial surface components after exposure to formaldehyde (HCHO) levels that decrease respiratory ciliary function. Bovine tracheae were reacted with an analog of N‐hydroxysuccinimidobiotin to label epithelial surface‐accessible components before exposure to HCHO. The tracheae were then exposed to 0, 16, 33, and 66 μg HCHO/cm2 epithelial surface for 30 min. Cilia were isolated from the epithelium, separated into membrane and internal axonemal portions, analyzed on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PACE), and either stained to detect proteins or transblotted to detect biotin‐labeled components. Densitometric analysis of axoneme proteins showed a decrease in the total amount extracted with increased HCHO concentration, including axoneme‐specific proteins, dynein, and tubulin. However, biotinylated proteins in the axoneme fractions proportionately increased. Membrane fractions showed little change in protein with increasing HCHO concentration. The majority of these is not biotin‐labeled and thus not surface‐accessible components. Biotinylated material in the membrane fractions showed a significant decrease with increased HCHO concentration, particularly of bands at 92, 98, and 105 kD. These data suggest that increasing HCHO exposure reduces both extractable ciliary axonemes and detergent‐soluble surface components, possibly by stabilizing respiratory epithelial membranes. This process apparently strengthens association of certain surface components with the internal axoneme, thereby reducing subsequent solubilization in detergent.