The brain-to-blood efflux transport of taurine and changes in the blood-brain barrier transport system by tumor necrosis factor-alpha

Abstract

The purpose of this study was to examine whether the efflux transport system for taurine from brain to blood is present at the blood-brain barrier (BBB) by using the brain efflux index (BEI) method and to determine whether the taurine transport system is regulated after central nervous system cell damage by tumor necrosis factor-alpha (TNF-alpha) in vivo. [H-3]Taurine was microinjected into the parietal cortex area 2 of the rat brain, and was eliminated from the brain with an efflux transport rate of 1.22 x 10(-2) min(-1), and the process is saturable with a K-m of 39.1 muM. This process was significantly inhibited by taurine transporter (TAUT) inhibitors, such as unlabeled taurine, beta-alanine, betaine, nipecotic acid and gamma-aminobutyric acid (GABA). In addition, the effect of tumor necrosis factor-alpha on [H-3]taurine transport was investigated. [H-3]Taurine uptake was increased and its efflux was reduced by pretreatment with tumor necrosis factor-alpha. Also, [H-3]taurine efflux was reduced by tumor necrosis factor-alpha in a time- and dose-dependent manner. In conclusion, there is the efflux pump for taurine at the blood-brain barrier to reduce taurine concentration in the brain interstitial fluid, and this process was carrier mediated. In addition, the transport system for taurine through the blood-brain barrier was found to be regulated by tumor necrosis factor-alpha in vivo. (C) 2004 Elsevier B.V. All rights reserved.