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KMID : 0390119940340010173
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Journal of Pusan Medical College
1994 Volume.34 No. 1 p.173 ~ p.182
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Characteristics of C-glutamate Uptake and Effect of Harmaline in Cat Brain Cortical Synaptosome
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Abstract
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Characteristics of 14C-glutamate uptake and the effect of harmaline were studied in synaptosomes isolated from cat brain cortex.
@ES The results were as follows:
@EN 1. Synaptosomal 14C-glutamate uptake was stimulated in the presence of NaCI in incubation medium. The uptake was increased by raising the concentrationof NaCI to 100 mM, and the half maximum uptake was observed at 32.4±4.7mM.
2. The synaptosomal 14C-glutamate uptake was decreased by replacement of Na+ with choline, K+, Li+ or Rb+ and also bythe replacemtn of CI+with NO3, SO42+ or SCN.
3. Kinetic analysis of the synaptosomal 14C-glutamate uptake showed an apparent Km of 14.6±1.8μM and Vmax of 642±32.4 pmole/ml protein/min.
4. Harmaline showed a mixed type inhibitionon the synaptosomal 14C-glutamate uptake with 50% inhibition at 1.2×10-5M. The inhibitory effect of harmaline was decreased by raising the concentration of Na+ in incubation medium.
5. Harmaline inhibited synaptosomal Na-K-ATPase activity in a dose-dependent manner with 50% inhibition at 3.2×10-4M.
From above results, it might be indicated that a Na-dependent high affinity glutamate transport system exists in the synaptosomal membrane of cat brain cortex, and harmaline inhibits it by competitive interaction with Na+.
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