[Study on the effect of hypergravity stress on L-glutamate uptake by rat brain nerve endings].
Using rat brain synaptosomes, we have investigated the effect of hypergravity on the kinetic parameters of Na(+)-dependent, high-affinity L-glutamate transport activity. The time-course of L-[14C]-glutamate uptake and dependence of L-[14C]-glutamate uptake velocity on glutamate concentrations were analyzed. K(m) and Vmax of this process have been determined. The hypergravity stress was created by centrifugation of rats for 1 hour at 10 g. We observed no differences in K(m) values between the control rats (10.7 +/- 2.5 microM) and animals exposed to hypergravity (6.7 +/- 1.5 microM). The similarity of this parameter for the two studied groups of animals showed that affinity of glutamate transporter to substrate was not sensitive to hypergravity stress. In contrast, the maximal velocity of glutamate uptake changed in hypergravity conditions. Vmax reduced from 12.5 +/- +/- 3.2 nmol/min per 1 mg of protein (control group) to 5.6 +/- 0.9 nmol/min per 1 mg of protein (animals, exposed to hypergravity stress). The possible mechanisms of attenuation of the glutamate transporter activity without modifying K(m) of glutamate uptake were discussed.
Borisova
T A
TA
Palladin Institute of Biochemistry, NAS of Ukraine, Kyiv. tborisov@paladin.biochem.kiev.ua
Krysanova
N V
NV
Himmelreĭch
N H
NH
D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D018698:Glutamic Acid / Q000493:pharmacokinetics*; D018471:Hypergravity; D007700:Kinetics; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000378:metabolism*
D018698:Glutamic Acid