Hexosamines VOLUME

When 1.5 volumes acetone is added to the trichloroacetic acid filtrate of the gastric juice, an abundant flocculent precipitate forms, which contains all the components of dissolved mucin with the exception of soluble mucus. If this precipitate is taken up in dilute alkali and then acidified with dilute HCl down to pH 3.5, a fine flocculent precipitate forms, which we named dissolved mucoprotein (G27, G36). It was later renamed glandular mucoprotein (G9, G38) because of its close relationship to the fundic glands of the stomach. This material contained much protein its nitrogen content was 12.61 0.44% and its tyrosine content 7.50 0.65% by the Folin-Giocalteu reaction. The reducing substance content was 6.38 1.48% before and 12.5% after hydrolysis (G9, G27, G36) (see Table 4). Werner (W9) determined the composition of this mucoprotein fraction and found that it contained 11.2% N by Kjeldahl, 8.8% hexosamine, 4.8% uronic acid, and 2.0% sialic acid. 

I performed the usual three-period experiments, irrigating pouches with 100 mN HCl in the first and second periods and with 1, 2, and 4 M urea in phosphate buffer, pH 7.4, in the third. The urea solutions were less hypertonic than FitzGerald s. During the period of urea irrigation the mucosa shed 3 to 8 ml of fluid in 30 minutes, not a large volume compared with that shed in other circumstances. It also shed mucus, for the solutions recovered were opaque and viscous. In control experiments with phosphate buffer alone the mucosa shed only 0.3 to 0.5 mg of hexosamines contained in mucus, but during the urea periods it shed 2.6 to 4.5 mg. Less than 20% of the urea was absorbed, and less than 3% was converted to the ammonia that appeared in the irrigation fluid. As expected, far more disappeared in the third than in the first period. Urea had broken the barrier. ... 

---