Glycosaminoglycans in rat mucosal mast cells

Rats were infected with the nematode Nippostrongylus brasiliensis, resulting in an approx. 5-fold increase in the number of mucosal mast cells and the histamine content of the intestinal (jejunum) wall. After injection of the infected animals with inorganic [35S]sulphate, a similar increase in the yield of labelled intestinal glycosaminoglycans was observed, compared with uninfected control rats. Autoradiography showed a highly selective labelling of the numerous mucosal mast cells and of the few connective-tissue mast cells in the subserosal region of the bowel. Analysis of the labelled polysaccharide from the infected animals showed that almost 60% of this material consisted of oversulphated galactosaminoglycan, whereas heparin-related polysaccharides accounted for only 13%. The galactosaminoglycan contained 4-monosulphated and 4,6-disulphated N-acetylgalactosamine residues in approx. 5:1 molar ratio, both being linked to D-glucuronic acid residues; the occurrence of L-iduronic acid units could not be excluded. No significant difference in structure was found between this polysaccharide and the corresponding component isolated from uninfected rats. It is concluded that the major polysaccharide produced by rat mucosal mast cells in vivo is an oversulphated galactosaminoglycan rather than heparin.