Mucus turnover rate

Mucus turnover rate. The turnover rate of the mucus layer is another physiological factor that affects mucoadhesion. Mucus turnover limits the potential duration of adhesion at the desired site of application. Within the GI tract, mucus is lost continuously secondary to enzymatic degradation (pepsin, lysosomal enzymes, and pancreatic enzymes), acid... 

Among these thiolated chitosans, chitosan-MNA showed the highest mucoadhesive features [33]. Even though thiolated chitosans have shown excellent mucoadhesive properties, the adhesion of the polymers is sloughed off by the natural mucus turnover due to a continuous process of mucus secretion. In the human intestine, for instance, the mucus turnover rate is typically about 12—24 h this is very rapid and makes it difficult for the polymers to interact with the mucosa for a prolonged period of time [34]. 

Attempts were also made to estimate the rate of turnover of the mucus gel. Telnet al. [14] measured the amount of mucus produced per time imit, using an in situ perfused intestinal loop model in the rat. They foimd that this turnover time is varying between 0.8 and 4.5 hr. 

Several techniques have been used to estimate the rate of mucus secretion, but their accuracy seems to be doubtful. Nevertheless, it has been concluded that a slow baseline secretion of mucus is maintained by exocytosis from goblet cells in the gastrointestinal tract, which appears to be under cholinergic control. Rubinstein and Tirosh used carbachol (cholinergic agonist) at different doses to increase the mucus thickness in different parts of the gastrointestinal tract. Attempts were also made to estimate the rate of turnover of the mucus gel. Lehr et al. measured the amount of mucus produced per time unit, using an in situ perfused intestinal loop model in the rat. They found that this turnover time varies between... 

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