The present study describes a simple and efficient method utilizing high performance liquid chromatography
(HPLC) coupled to fluorescence detection for the determination of kinetic parameters of glutamate
uptake in nervous tissue. Retinal tissue obtained from 7-day-old chicks was incubated with known concentrations
of glutamate (50–2000 M) for 10 min, and the levels of the o-phtaldehyde (OPA)-derivatized
neurotransmitter in the incubation medium were measured. By assessing the difference between initial
and final concentrations of glutamate in the medium, a saturable uptake mechanism was characterized
(Km = 8.2 and Vmax = 9.8 nmol/mg protein/min). This measure was largely sodium- and temperaturedependent,
strongly supporting that the mechanism for concentration decrements is indeed uptake by
high-affinity transporters. Added to this, our results also demonstrated that zinc chloride (an inhibitor
of glutamate/aspartate transporters) evoked a concentration-dependent decrease in glutamate uptake,
demonstrating the specificity of our methodology. Overall, the present work characterizes an alternative
methodology to evaluate glutamate uptake in nervous tissue using HPLC. This approach could be an
important tool for studies associated to the characterization of minute alterations in glutamate transport
related with central nervous system injury.
The present study describes a simple and efficient method utilizing high performance liquid chromatography(HPLC) coupled to fluorescence detection for the determination of kinetic parameters of glutamateuptake in nervous tissue. Retinal tissue obtained from 7-day-old chicks was incubated with known concentrationsof glutamate (50–2000 M) for 10 min, and the levels of the o-phtaldehyde (OPA)-derivatizedneurotransmitter in the incubation medium were measured. By assessing the difference between initialand final concentrations of glutamate in the medium, a saturable uptake mechanism was characterized(Km = 8.2 and Vmax = 9.8 nmol/mg protein/min). This measure was largely sodium- and temperaturedependent,strongly supporting that the mechanism for concentration decrements is indeed uptake byhigh-affinity transporters. Added to this, our results also demonstrated that zinc chloride (an inhibitorof glutamate/aspartate transporters) evoked a concentration-dependent decrease in glutamate uptake,demonstrating the specificity of our methodology. Overall, the present work characterizes an alternativemethodology to evaluate glutamate uptake in nervous tissue using HPLC. This approach could be animportant tool for studies associated to the characterization of minute alterations in glutamate transportrelated with central nervous system injury.
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