Serum amino acid levels after permanent middle cerebral artery occlusion in the rat.

BACKGROUND AND PURPOSE

High levels of glutamate in plasma and cerebrospinal fluid (CSF) have been demonstrated in patients with acute ischemic stroke. Whereas this glutamate increase in CSF is only evidenced during the first 6 h in stable ischemic stroke, it is sustained for 24 h in progressing stroke. The aim of this investigation was to study the evolution of serum glutamate levels after stroke in a rat model of permanent cerebral artery occlusion.

METHODS

Glutamate, glycine, aspartate, taurine and tryptophan were measured by high-performance liquid chromatography from serum samples taken before and at different times after permanent middle cerebral artery occlusion (MCAO) and from sham-operated rats.

RESULTS

After MCAO, a 3-fold increase in glutamate and a 2-fold increase in glycine and aspartate were observed in rat serum. The onset of this amino acid increase began 4-6 h after ischemic induction, reached peak values at 8-24 h and returned to preischemic values by 48-72 h. Serum concentrations of taurine and tryptophan were not modified after MCAO. Sham-operated rats did not exhibit changes of basal amino acid concentrations in serum.

CONCLUSIONS

The serum excitatory amino acid profile in this experimental model confirms that the early detection of increased concentrations of glutamate and glycine at systemic circulation observed in patients with acute stroke is a consequence of the cerebral ischemic process.