High-affinity uptake of taurine and ?-alanine in primary cultures of rat astrocytes

Abstract

The kinetics and specificity of taurine and β-alanine uptake were studied in primary cultures of rat astrocytes under identical experimental conditions. The uptake consisted of nonsaturable penetration and saturable high-affinity transport that was strictly sodium dependent. The cells accumulated taurine more effectively than β-alanine, both the affinity and uptake capacity being greater for taurine. Taurine uptake was competitively inhibited by β-alanine and GABA, the former being more potent. Also, hypotaurine and 2-guanidinoethanesulphonic acid strongly reduced taurine uptake, but L-2,4-diaminobutyric acid had no significant effect. β-Alanine uptake was also competitively inhibited by GABA, but the most potent inhibitors were hypotaurine and 2-guanidinoethanesulphonic acid.l-2,4-Diaminobutyric acid was moderately active. The uptake systems for taurine and β-alanine were thus in principle similar, and they exhibited certain characteristics typical for a neurotransmitter amino acid. The inhibition studies further suggest the existence of only one common transport system for taurine, β-alanine, and GABA in cultured primary astrocytes. The same uptake system may also be used for hypotaurine.