Behavior of mucus glycoproteins of tracheal secretory cells following L-cysteine methyl ester treatment

The effects of L-cysteine methyl ester on behavior of mucus glycoproteins in canine tracheal secretory cells were investigated histologically and histochemically. Low concentrations (10(-7) and 10(-6)M) of L-cysteine methyl ester produced, as histological changes, decreases in the total goblet cell number and the thickness of the acini of submucosal glands, and an increase in the acinar inner diameter. On the other hand, L-cysteine methyl ester at 10(-5) and 10(-4)M produced an increase in the thickness of the acini and a slight decrease in the acinar inner diameter. Both the total acid glycoprotein and sulphated glycoprotein contents in glandular cells markedly decreased, whereas the neutral glycoprotein content in the cells increased following L-cysteine methyl ester treatment in a concentration-dependent way. Total saccharide and protein concentrations in the incubation fluid increased with 10(-7) and 10(-6)M, but decreased with 10(-5) and 10(-4)M L-cysteine methyl ester. N-Acetylhexosamine concentration in the bathing fluid increased at 10(-7) and 10(-6)M of the agent. These findings suggest that low concentrations of L-cysteine methyl ester stimulate secretory activities of tracheal secretory cells, while at high concentrations the agent stimulates synthesis of mucus glycoproteins in the submucosal glands. Additionally, it is suggested that L-cysteine methyl ester has a marked viscosity lowering effect on the mucus in the secretory cells.