Transport of β-alanine in renal brush border membrane vesicles
Transport of β-alanine in renal brush border membrane vesicles
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β-丙氨酸在肾刷状缘膜囊泡中的转运
DOI：
10.1016/0005-2736(78)90052-4
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
B. Sacktor
中科院分区：
文献类型：
--
作者：
M. Hammerman;B. Sacktor
β-丙氨酸的平衡摄取随介质渗透压的增加而降低，与β-丙氨酸预孵育增加了氨基酸的摄取，这一发现表明兔肾刷状缘膜对β-丙氨酸的摄取代表转运至膜囊泡中。Na+电化学梯度（囊外>囊内）刺激β-丙氨酸摄取的初始速率约3倍，并实现氨基酸的瞬时积累，达到平衡值的两倍。钠离子的吸收刺激是特定的。短杆菌肽消除了过冲，可能是通过加速Na+通过不与β-丙氨酸摄取偶联的途径进入囊泡的生电入口来消散梯度。缬氨霉素可增强载钾囊泡对β-丙氨酸的Na+依赖性摄取。这些结果表明，β-丙氨酸的Na+梯度依赖性转运是一个产电过程，并表明膜电位是β-丙氨酸转运的决定因素。在给定浓度下，β-苯胺的摄取反映了Na+梯度依赖性和非依赖性转运系统的贡献之和。依赖性系统在100 μM时饱和。独立系统没有饱和。在生理浓度下，Na+梯度依赖性摄取的速率是在没有梯度的情况下的四倍。牛磺酸强烈抑制β-丙氨酸摄取的Na+梯度依赖性速率，表明β-氨基酸具有共同的转运系统，α-氨基酸，即L-精氨酸、L-谷氨酸、L-脯氨酸和甘氨酸，代表先前报道的刷状缘膜中的特异性α-氨基酸转运系统，不抑制β-丙氨酸的摄取。这些发现表明刷状缘膜具有独特的β-氨基酸转运系统。
The findings that the equilibrium uptake of β-alanine decreased with increasing medium osmolarity and preincubation with β-alanine increased uptake of the amino acid indicate that the uptake of β-alanine by rabbit renal brush border membranes represents transport into membrane vesicles. A Na+electrochemical gradient (extravesicular > intravesicular) stimulated the initial rate of β-alanine uptake about three times and effected a transient accumulation of the amino acid twice the equilibrium value. Stimulation of the uptake was specific for Na+. Gramicidin abolished the overshoot, presumably by dissipating the gradient by accelerating the electrogenic entrance of Na+into the vesicle via a pathway not coupled to uptake of β-alanine. In K+-loaded vesicle, valinomycin enhanced the Na+gradient-dependent uptake of β-alanine. These findings indicate that the Na+gradient-dependent transport of β-alanine is an electrogenic process and suggest that the membrane potential is a determinant of β-analine transport. Uptake of β-aniline, at a given concentration, reflected the sum of contributions from Na+gradient-dependent and -independent transport systems. The dependent system saturated at 100 μM. The independent system did not saturate. At physiological concentrations the rate of the Na+gradient-dependent uptake was four times that in the absence of the gradient. The Na+gradient-dependent rate of β-alanine uptake was strongly inhibited by taurine, suggesting that β-amino acids have a common transport system, α-Amino acids, i.e.l-arginine,l-glutamate,l-proline, and glycine, representing previously reported specific α-amino acid transport systems in the brush border membrane, did not inhibit the uptake of β-alanine. These findings indicate that the brush border membrane has a distinct transport system for β-amino acids.