Region-specific distribution of glycosphingolipids in the rabbit gastrointestinal tract: preferential enrichment of sulfoglycolipids in the mucosal regions exposed to acid.

Neutral and acidic glycosphingolipids from various regions of the rabbit gastrointestinal tract showed different but characteristic patterns. In particular, sulfatides were found to be present in high concentrations in the mucosal regions frequently exposed to gastric acid, such as the gastric mucosa and proximal intestinal mucosa (duodenum and jejunum). The majority of sulfatides in these tissues have been identified as GalCer-I3-sulfate, with alpha-hydroxy long-chain fatty acids, by chemical procedures including analysis by negative ion fast atom bombardment mass spectrometry. The concentrations of GalCer-I3-sulfate in the fundic mucosa, antral mucosa, duodenum, and jejunum were 394.0, 356.9, 829.3, and 378.1 nmol/g of dry weight, respectively. These concentrations exceed those in the kidney, which has been reported to contain the highest concentration of sulfatides, with the exception of the nervous system, also, especially in the fundic mucosa, gangliosides were drastically reduced, in contrast to sulfatides: the molar ratio of sulfatides to GM3, the major ganglioside, was about 11:1. In addition, in the acid hydrolysis experiment, using the same concentration of HCl as that present in the gastric juices, sulfatide proved to be much more resistant to acid than GM3. Therefore, the preferential distribution of sulfatides in the mucosal regions exposed to acid may be related to mucosal functions, such as acid secretion and protection from acidic environments.