Variability in brain ganglioside content and composition of endothermic mammals, heterothermic hibernators and ectothermic fishes.

Content and composition of brain gangliosides were compared among endothermic mammals, heterothermic hibernators and ectothermic fishes from habitats with extreme ambient temperatures (tropic vs. antarctic waters). In general the content of brain gangliosides in fishes is significantly lower and exhibits a greater variability than in mammals. The composition of brain gangliosides was investigated using both one- and two-dimensional High Performance Thin Layer Chromatography (HPTLC). Both techniques showed a remarkable increase in the number of individual ganglioside fractions and an additional increase of higher polar fractions in fishes as compared with mammals. The 2D-HPTLC revealed a significant decrease in the relative proportion of alkali-labile gangliosides in the course of evolution from fish to mammals. Moreover this decrease in alkali-lability is correlated with the state of thermal adaptation (antarctic fishes, 53-66%; tropical cichlid fish, 35%). These results provide additional evidence for the notion that the extremely high polarity of brain gangliosides, especially of cold-blooded vertebrates, reflects a very efficient mechanism on the molecular level to keep the neuronal membrane functional under low temperature conditions.