Discrimination of parallel neutral amino acid transport systems in the basolateral membrane of cat salivary epithelium.
Discrimination of parallel neutral amino acid transport systems in the basolateral membrane of cat salivary epithelium.
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猫唾液上皮基底外侧膜平行中性氨基酸转运系统的区分。
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
D. Yudilevich
中科院分区：
文献类型：
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作者：
G. Mann;D. Yudilevich
用快速(不超过30 S)单循环成对示踪稀释法研究了短链和长链中性氨基酸在猫唾液腺灌流过程中跨上皮基侧膜的转运。通过比较一种氚氨基酸和D-[14C]甘露醇(细胞外参照物)的静脉稀释曲线来测量氨基酸摄取。根据最大示踪剂摄取量(Umax)、灌流液流量(F)和灌流液氨基酸浓度(Ca)估算单向内流(V)：V=[-F]。Ln(1-Umax)]。加州L-丙氨酸内流是可饱和的，且明显由单通道系统调节(Km=0.83+/-0.11 mm，Vmax=655+/-32nmol/min)。g)。这些动力学常数比我们以前报道的L-苯丙氨酸的Km=6.4 mm和Vmax=1719nmol/min要低得多。在很宽的浓度范围内(0.05-24 mM)进行的交叉抑制实验中，可以进一步区分L-丙氨酸和L-苯丙氨酸的流入，因为L-苯丙氨酸(Ki=22 mM)和L-丙氨酸(Ki=19 mM)都表现出较差的竞争对手。清除灌流液中的Na+可选择性地抑制L-丙氨酸和L-丝氨酸的内流，而长链中性氨基酸L-亮氨酸、L-苯丙氨酸和L-色氨酸的内流不受影响。腺体长时间灌流二硝基苯酚(0.8 mM，20-30分钟)，虽然对单向摄取有不同程度的抑制作用，但显著增加了L亮氨酸、L苯丙氨酸、L酪氨酸和碱性氨基酸L赖氨酸的示踪外流。似乎至少有两个独立的中性氨基酸转运系统在唾液上皮的血-组织界面上起作用：(I)依赖Na+的丙氨酸-丝氨酸-半胱氨酸载体类型，表现出对具有短、极性或线性侧链的氨基酸的高亲和力；(Ii)Na+非依赖性亮氨酸载体类型，选择性地选择大的中性氨基酸。
Transport of short‐chain and long‐chain neutral amino acids across the basolateral membrane of the epithelium in the perfused cat salivary gland has been studied using a rapid (less than 30 s) single circulation paired‐tracer dilution technique. Amino acid uptake was measured by comparing the venous dilution profiles for a tritiated amino acid and D‐[14C]mannitol (extracellular reference) following a bolus intra‐arterial injection of a mixture containing both molecules. Unidirectional influx (v) was estimated from the maximal tracer uptake (Umax), the perfusate flow (F) and the perfusate amino acid concentration (Ca): v = [‐F . ln (1‐Umax)] . Ca. L‐alanine influx was saturable and apparently mediated by a single entry system (Km = 0.83 +/‐ 0.11 mM and Vmax = 655 +/‐ 32 nmol/min . g). These kinetic constants were considerably lower than our previously reported values for L‐phenylalanine: Km = 6.4 mM and Vmax = 1719 nmol/min . g. In cross‐inhibition experiments performed over a wide range of concentrations (0.05‐24 mM), influx of L‐alanine and L‐phenylalanine could be further discriminated, since both L‐phenylalanine (Ki = 22 mM) and L‐alanine (Ki = 19 mM) behaved as poor competitors. Removal of Na+ from the perfusate resulted in a selective inhibition of L‐alanine and L‐serine influx, whereas influx of the long‐chain neutral amino acids L‐leucine, L‐phenylalanine and L‐tryptophan remained unaffected. Although prolonged perfusion of glands with dinitrophenol (0.8 mM for 20‐30 min) caused a variable but net inhibition of unidirectional uptake, it markedly enhanced the tracer efflux of L‐leucine, L‐phenylalanine, L‐tyrosine and the basic amino acid L‐lysine. It appears that at least two separate neutral amino acid transport systems are operative at the blood‐tissue interface of the salivary epithelium: (i) a Na+‐dependent alanine‐serine‐cysteine preferring type of carrier exhibiting a high affinity for amino acids with short, polar or linear side chains and (ii) a Na+‐independent leucine preferring type of carrier selective for large neutral amino acids.
肾源性上皮细胞系 (LLC-PK1) 的极化氨基酸转运。
DOI：
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发表时间：
1982
期刊：
The Journal of biological chemistry
影响因子：
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作者：
Rabito,CA;Karish,MV
通讯作者：
Karish,MV