Chesney R W, Jax D K
Biochim Biophys Acta. 1977 Apr 1;466(1):84-96. doi: 10.1016/0005-2736(77)90210-3.
Taurine, a naturally found beta-amino acid, is inert in rat renal cortex slices. Its active accumulation by slices is abolished by anaerobiosis, a strongly acidic media or the removal of Na+. Concentration-dependent uptake studies reveal more than one taurine carrier: the apparent Km value for uptake below 1.1 mM is 0.4 mM and the apparent Km value above 1.1 mM is 14.5 mM. Of all amino acids tested only beta-alanine, another beta-compound, inhibited uptake. The oxidizing agent diamide was used to lower the concentration of GSH in rat cortex slices. The ability to accumulate taurine by the low Km system was decreased in diamide-treated slices, but not by the high Km system. Diamide was found to greatly augment efflux of taurine taken up from lower concentrations but not from higher concentrations. GSH in the media prevented this diamide-induced inhibition of uptake and enhanced efflux at lower taurine concentrations. A possible mechanism of diamide inhibition of uptake is that intracellular GSH depletion leads to greatly enhanced efflux of taurine, thus preventing uptake.
牛磺酸是一种天然存在的β-氨基酸，在大鼠肾皮质切片中呈惰性。切片对其主动摄取会因厌氧、强酸性介质或去除钠离子而被消除。浓度依赖性摄取研究揭示了不止一种牛磺酸载体：摄取低于1.1 mM时的表观Km值为0.4 mM，高于1.1 mM时的表观Km值为14.5 mM。在所有测试的氨基酸中，只有另一种β化合物β-丙氨酸抑制摄取。氧化剂二酰胺用于降低大鼠皮质切片中谷胱甘肽（GSH）的浓度。经二酰胺处理的切片中，低Km系统积累牛磺酸的能力降低，但高Km系统未受影响。发现二酰胺能极大地增加从较低浓度摄取的牛磺酸的外排，但对较高浓度摄取的牛磺酸外排无影响。培养基中的GSH可防止二酰胺诱导的摄取抑制，并在较低牛磺酸浓度下增强外排。二酰胺抑制摄取的一种可能机制是细胞内GSH耗竭导致牛磺酸外排大大增强，从而阻止摄取。
