In Vitro Studies on the Putative Function of N-acetylaspartate as an Osmoregulator |
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Authors: | Mattias Tranberg Abdul-Karim Abbas Mats Sandberg |
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Affiliation: | 1.Institute of Neuroscience and Physiology, Department of Physiology,G?teborg University,G?teborg,Sweden;2.Institute of Biomedicine, Department of Medical Chemistry and Cell biology,G?teborg University,G?teborg,Sweden |
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Abstract: | Efflux and tissue content of N-acetylaspartate (NAA) and amino acids were evaluated from cultured and acutely prepared hippocampal slices in response to changes in osmolarity. The osmoregulator taurine, but not NAA, was lost from both types of slices after moderate reductions in extracellular osmolarity (−60 mOsm) for 10–48 h. Hypoosmotic shock (−166 mOsm) for 5 min resulted in unselective efflux of several amino acids from acutely prepared slices. Notably, the efflux of taurine, but not NAA, was prominent also after the shock. Efflux of NAA was markedly enhanced by NMDA and high K+, in particular after the stimulation period. The high K+-mediated efflux was decreased by high extracellular osmolarity and a NMDA-receptor antagonist. The results indicate that NAA efflux can be induced by a sudden non-physiological decrease in extracellular osmolarity but not by prolonged more moderate changes in osmolarity. The mechanisms behind the efflux of NAA by high K+ are complex and may involve both swelling and activation of NMDA-receptors. |
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Keywords: | N-acetylaspartate Creatine Taurine Hypotaurine HPLC Hippocampal slices Volume regulation Osmoregulator NMDA Depolarisation Amino acids |
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