A role of lysosomal enzymes in the mechanism of mucolytic action of bromhexine.

The effect of bromhexine on behaviors of lysosomal enzymes in the submucosal gland was investigated using canine tracheal slice preparations, with reference to the histochemical changes in acid glycoproteins (AGP) in the gland. Incubation of tracheal slices with 1% Triton X-100 or 0.0004-0.04% bromhexine for 30 min decreased the number of stained lysosomes in the glandular cells. The decrease in stained lysosomes after treatment with 1% Triton X-100 or 0.04% bromhexine was effectively prevented by addition of 5% lecithin. The number of glandular cells that were stained red (stain index R) in the combined alcian blue at pH 2.5 and periodic acid-Schiff procedure markedly increased by treatment with 1% Triton X-100 or 0.0004-0.04% bromhexine. In the bromhexine treated groups, there was a close correlation (r=0.932, P less than 0.01) between the increase in the number of glandular cells showing the stain index R and the decrease in the number of stained lysosomes in the cells. These findings suggest that the enzymes which are liberated from lysosomes into the cytoplasm by bromhexine may, at least in a part, be involved in the mucolytic action of the agent on AGP contained in mucus granules of the submucosal gland.