AN EXPERIMENTAL-MODEL FOR THE EXPOSURE OF HUMAN CILIATED CELLS TO SULFUR-DIOXIDE AT DIFFERENT CONCENTRATIONS

Mucociliary transport is an important nonimmunological defense mechani sm of the respiratory tract. The aim of this study was to investigate the effect of sulfur dioxide (SO2) at different concentrations on cili ary beat frequency (CBF). Ciliated cells were obtained from 12 volunte ers by nose brush. CBF was quantified using video-interference microsc opy. The cells were placed on a polycarbonate membrane in contact with the surface of a reservoir filled with RPMI 1640 (bicarbonate buffere d) or Ringer's (electrolyte) solution, allowing the cells to be suppli ed by capillarity. In an exposure chamber the cells were exposed for 3 0 min to SO2 2.5-12.5 ppm at 37 degrees C and 100% air humidity. SO2 i nduced a dose-dependent decrease in CBF of the cells cultured in Ringe r's solution. SO2 at 2.5 ppm caused a 32.8% decrease and at 12.5 ppm a 96.5% decrease (8.1 +/- 0.24 versus 0.28 +/- 0.20 Hz). CBF of cells c ultured in RPMI 1640 was reduced only moderately after 12.5 ppm SO2 ex posure (7.9 +/- 0.26 versus 6.70 +/- 0.30 Hz). In Ringer's solution a decrease in pH was observed after 30 min of SO2 exposure to 12.5 ppm t o a minimum value of 3.6. By contrast, the pH of RPMI 1640 remained co nstant at 7.5 under identical conditions. After adding RPMI 1640 to Ri nger's solution, CBF increased in parallel to the pH to control values (5.0 ppm: 4.64 +/- 0.45 to 8.51 +/- 0.60 Hz). These data suggest that the highly water-soluble SO2, reversibly eliminates CBF in correlatio n with a decrease in pH.