ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: The transport kinetics of γ-aminobutyric acid (GABA), taurine, and β-alanine in addition to the mutual inhibition patterns of these compounds were investigated in cultures of neurons and astrocytes derived from mouse cerebral cortex. A high-affinity uptake system for each amino acid was demonstrated both in neurons (KmGABA= 24.9 ± 1.7 μM; KmTau= 20.0 ± 3.3 μM; Kmβ-Ala= 73.0 ± 3.6 μM) and astrocytes (KmGABA= 31.4 ± 2.9 μM, KmTau= 24.7 ± 1.3 μM; Kmβ-Ala= 70.8 ± 3.6 μM). The maximal uptake rates (Vmax) determined were such that, in neurons, VmaxGABA〉 Vmaxβ-Ala=VmaxTau, whereas in astrocytes, Vmaxβ-Ala 〉 VmaxTau=VmaxGABA. Taurine was found to inhibit β-alanine uptake into neurons and astro cytes in a competitive manner, with Ki values of 217 μM in neurons and 24 μM in astrocytes. β-Alanine was shown to inhibit taurine uptake in neurons and astrocytes, also in a competitive manner, with Ki values of 72 μM in neurons and 71 μM in astrocytes. However, β-alanine was found to be a weak noncompetitive inhibitor of neuronal and astrocytic GABA uptake, whereas in reverse experiments, GABA displayed weak noncompetitive inhibition of neuronal and astrocytic uptake of β-alanine. Likewise, taurine was a weak noncompetitive inhibitor of GABA uptake in neurons and similarly, GABA was a weak noncompetitive inhibitor of taurine uptake into neurons. Taken together, the similarity between the results obtained for β-alanine and taurine uptake in addition to their competitive mode of mutual inhibition strongly suggest that these compounds share a common carrier in neurons and astrocytes and that neither amino acid in either cell type is transported appreciably, if at all, by the GABA carrier, and vice versa.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1986.tb04519.x
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