Higher expression of renal sulfoglycolipids in marine mammals

Patterns and contents of major acidic glycosphingolipids in the kidney of three marine mammalian species, the Steller sea lion (Pinnipedia), the rough-toothed dolphin and the broad-beaked dolphin (Odontoceti), were examined, and compared with those of terrestrial mesic mammals. The profile of major acidic glycosphingolipids was not significantly different between the terrestrial and marine mammals: predominant gangliosides were GM3 and GD3, and major sulfoglycolipids were SM4s and SM3. On the other hand, the total concentration (nmol/g wet tissue) of sulfoglycolipids was considerably higher in the marine mammals (2.3–3.0 times) than that in the terrestrial mesic mammals with comparable body weights. In contrast, there was no significant difference in the level of renal glycolipids-bound sialic acid between the marine and the terrestrial mammals. These results suggest that higher expression of renal sulfoglycolipids in marine mammals may contribute to the maintenance of osmotic balance of their body fluid against sea water.