Effect of Exogenous Gangliosides on Amino Acid Uptake and Na+,K+‐ATPase Activity in Superior Cervical and Nodose Ganglia of Rats

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Abstract
The effects of some gangliosides on active uptake of nonmetabolizable a-aminoisobutyric acid (AIB) and Na+,K+-ATPase and Ca2+,Mg2+-ATPase activities in superior cervical ganglia (SCO) and nodose ganglia (NG) excised from adult rats were examined during aerobic incubation at 37°C for 2 h. In NG, amino acid uptake was greatly acceler-a.ed with addition of galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosyl ceramide (GM1) (85%) and also with N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosyl ceramide (GM2) or [N-acetylneuraminyl]-galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosyl ceramide (GD1a) (43% each) compared with a nonaddition control at a 5 nM concentration. Under identical conditions, Na+,K+-ATPase activity was strongly stimulated with GM1 (180%) and GD1a (93%), whereas Ca,Mg2+-ATPase activity showed no change. In SCG, on the other hand, AIB uptake was apparently inhibited (-27%) by addition of GM1, with a slight decrease in Na+,K+-ATPase but no change in Ca2+,Mg2+-ATPase activity in the tissue. Both asialo-GM1, in which W-acetylneuraminic acid is deficient, and Forssman glycolipid, which is not present in nervous tissue, failed to produce any significant increase in both SCG and NG not only in amino acid uptake, but also in Na+,K+-ATPase activity. A kinetic study of active AIB uptake showed that GM1 ganglioside produced an increase in Km with no change in Vmax in SCG, whereas it caused a decrease in Km with a slight increase in Vmax in NG. Treatment of NG and SCG with neuraminidase from Vibrio cholerae, an enzyme that split off sialic acid from polysialoganglioside, leaving GM1 intact, caused little inhibition of the amino acid uptake. GM1-evoked amino acid uptake increase in NG and decrease in SCG seem both to be independent of the effect of nerve growth factor (NGF). Glia maturation factor (GMF)-induced AIB uptake was further increased by GM1 application in NG. These results suggest that exogenous brain gangliosides may modulate membrane transport of amino acid by processes somewhat different from those of NGF or GMF, with or without affecting the activity of a transport enzyme, Na+,K+-ATPase.