L- [14С] -glutamate uptake by nerve terminals from rat cerebellum and cerebral hemispheres under artificial hypergravity

1Borisova, TA, 1Krisanova, NV, 2Himmelreich, NH
1Palladin Institute of Biochemistry of National Academy of Sciences of Ukraine, Kyiv, Ukraine
2O.V. Palladin Institute of Biochemistry of the NAS of Ukraine, Kyiv, Ukraine
Kosm. nauka tehnol. 2002, 8 ;(1):101-106
Publication Language: Українська
Using synaptosomes from rat cerebellum and cerebral hemispheres, we investigated the effect of hypergravity on the kinetic parameters Км and Vmax of the Na+-dependent, high-affinity L- [14С] -glutamate transport activity. The hypergravity stress was created by centrifugation of rats for 1 hour at 10g. We observed no differences in  Км values for cerebellum and cerebral hemisphere synaptosomes between the control rats — 18.2±7.6 μM (cerebellum), 10.7± ±2.5 μM (cerebral hemispheres) and the animals exposed to hypergravity — 23.3± 6.9 μM (cerebellum), 6.7±1.5 μM (cerebral hemispheres). The similarity of this parameter for the two groups of animals showed that the affinity of glutamate transporter to substrate in cerebellum and cerebral hemispheres was not sensitive to hypergravity stress. The maximal velocity of  L- [14С] -glutamate uptake (Vmax) diminished for cerebellum synaptosomes from 9.6±3.9 nmol/min/mg of protein in the control group to 7.4±2.0 nmol/min/mg of protein in the animals exposed to hypergravity stress and for cerebral hemisphere synaptosomes from 12.5±3.2 nmol/min/mg of protein to 5.6±0.9 nmol/min/mg of protein, respectively. It was also shown that the hypergravity effect on the level of L- [14С] -glutamate uptake was different for cerebellum and cerebral hemisphere synaptosomes. Only for cerebellum synaptosomes, a significant decrease in the level of L- [14С] -glutamate uptake was observed. Possible mechanisms of the attenuation of glutamate transporter activity are discussed.
Keywords: glutamate transporter, hypergravity stress, synaptosomes
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