ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
It was found that rat brain nerve endings contain a high affinity and Na- dependent transport system for [3H]β-alanine ([3H]β-ala). As determined from Michaelis-Menten plots, the [3H]β-ala Km was 2.8 × 10-5 M and the Vmax was 0.29 nmol/mg protein/5 min. Under similar incubation conditions the [3H]GABA Km was 3.8 x 10-6M and the Vmax was 6.3 nmol/mg protein/5 min. The [3H]β-ala and [3H]GABA transport systems were further characterized by determining the IC50 values for a number of compounds. The compounds tested were GABA, β-ala, l-2,4-diaminobutyric acid. DL-3-hyd-roxy-GABA, β-guanidopropionic acid, strychnine, γ-guanidobutyric acid, imidazole-4-acetic acid, DL-proline, bicuculline, L-serine, glycine, l-α-ala and taurine. DABA, dl-3-hydroxy-GABA, β-guanidopro-pionic acid and γ-guanidobutyric acid were more potent inhibitors of [3H]GABA than [3H]β-ala transport. Strychnine, imidazole-4-acetic acid, proline and glycine were between 2 and 6 times more potent inhibitors of [3H]β-ala than [3H]GABA transport. β-Ala, bicuculline, serine, α-alanine and taurine were all markedly more potent (12–150 times) inhibitors of [3H]β-ala than [3H]GABA transport. IC50 values were also determined for the above compounds for the sodium-dependent and the sodium-independent binding of [3H]GABA to both fresh and frozen brain membranes. In general, the potency of these compounds to inhibit either sodium-independent or sodium-dependent binding was greater in fresh tissue. It was also observed that the neurophysiologically‘glycine-like’amino acids were more potent inhibitors in the presence of NaCl. No significant correlations were found between [3H]GABA binding under any condition and [3H]GABA or [3H]β-ala transport into nerve endings.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1978.tb06552.x
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