Effect of SO2 exposure on nasal mucociliary clearance in intact chickens

The time required for mucociliary clearance from the chicken nasal turbinate and from the maxillary sinus was investigated in individual animals by using a newly designed plastic holder for the experimental animals. Determined in this way were: 1) the effect of SO2 exposure on sinus and turbinate clearance time, 2) the effect of the nerve blocking drugs atropine, scopolamine, reserpine, and propranolol on turbinate clearance time, and 3) the effect of these nerve blockers on clearance rates in chickens exposed to SO2. Turbinate mucociliary clearance was measured at 5 intervals per day, during 1 to 7 hr after exposure, for 7 consecutive days. Sinus clearance time was measured twice daily 1 to 4 hr after exposure. Turbinate clearance time in birds exposed to 6 ppm, and sinus clearance time in birds exposed to 40 ppm intermittently for 2 consecutive days both increased strikingly as a direct effect of SO2 exposure. However, continuous exposure to 6 ppm of SO2 during 16 hr per day for 7 consecutive days produced double peaks of increased turbinate clearance time with intervening recovery periods, suggesting an intranasal mucociliary homeostatic response. In individual animals, 26 of 35 animals (75%) exposed to 5 ppm, and 5 of 10 animals (50%) exposed to 20 ppm continuously during 16 hr per day for 7 consecutive days showed the same patterns. Reserpine and propranolol, which are sympatholytic agents, produced decelerated intranasal transport rates. Atropine and scopolamine, which are parasympatholytic agents, did not affect clearance rates. These nerve blockers, however, blocked the biphasic recovery pattern due to SO2 exposure. This blocking effect was statistically significant for atropine and reserpine 1 hr after injection.