VARIABILITY IN BRAIN GANGLIOSIDE CONTENT AND COMPOSITION OF ENDOTHERMIC MAMMALS, HETEROTHERMIC HIBERNATORS AND ECTOTHERMIC FISHES

Content and composition of brain gangliosides were compared among endo thermic mammals, heterothermic hibernators and ectothermic fishes from habitats with extreme ambient temperatures (tropic vs. antarctic wate rs). In general the content of brain gangliosides in fishes is signifi cantly lower and exhibits a greater variability than in mammals. The c omposition of brain gangliosides was investigated using both one- and two-dimensional High Performance Thin Layer Chromatography (HPTLC). Bo th techniques showed a remarkable increase in the number of individual ganglioside fractions and an additional increase of higher polar frac tions in fishes as compared with mammals. The 2D-HPTLC revealed a sign ificant decrease in the relative proportion of alkali-labile gangliosi des in the course of evolution from fish to mammals. Moreover this dec rease in alkali-lability is correlated with the state of thermal adapt ation (antarctic fishes, 53-66%; tropical cichlid fish, 35%). These re sults provide additional evidence for the notion that the extremely hi gh polarity of brain gangliosides, especially of cold-blooded vertebra tes, reflects a very efficient mechanism on the molecular level to kee p the neuronal membrane functional under low temperature conditions.