Barbiturate inhibition of GLUT-1 mediated hexose transport in human erythrocytes exhibits substrate dependence for equilibrium exchange but not unidirectional sugar flux.
Barbiturate inhibition of GLUT-1 mediated hexose transport in human erythrocytes exhibits substrate dependence for equilibrium exchange but not unidirectional sugar flux.
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巴比妥对人红细胞中 GLUT-1 介导的己糖转运的抑制表现出平衡交换的底物依赖性，但不是单向糖通量。
DOI：
10.1021/bi962050f
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Haspel,HC
中科院分区：
文献类型：
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作者：
el-Barbary,A;Fenstermacher,JD;Haspel,HC
巴比妥酸盐在体内抑制GLUT-1介导的己糖转运体[Gjedde&Rasmussen(1980)J.NeuroChem.35,1382−1387；Otsuka.等人(1991年)am.J.Physiol.261，R265−R275]和体外[Honkanenet al.(1995)BioChemical 34,535−544]。在这项研究中，巴比妥酸盐抑制GLUT-1介导的己糖转运的机制是通过测量功能良好的富含GLUT-1的人红细胞系统中己糖的单向零转运和平衡交换通量来检验的。10 mM的戊巴比妥(PB)对单向内流和外流均有抑制作用(~gt；80%)。PB对单向通量的对称抑制几乎与顺式糖浓度无关(2−130 mM)，其IC50为∼2 mM。与单向糖通量相反，PB对平衡交换糖通量的抑制随底物浓度的增加而减弱(例如，在1 mM GLC时抑制88%，而在10 mM GLC时抑制40%)，并在100 mM GLC时表现出∼10 mM的IC50值。其他巴比妥酸盐被发现以这种不同的方式抑制人类红细胞中的糖流动。这些发现，当与为GLUT-1介导的转运提出的动力学模型一起看待时[Carruthers(1990)Physiol。Rev.70,1135−1176]，与巴比妥酸盐一致，巴比妥酸盐是Glc转位的非竞争性抑制剂，并优先抑制载体蛋白的未占据形式。因此，我们认为巴比妥酸盐可以防止或改变与膜内载体蛋白重新定向相关的构象变化。总体而言，这些结果表明，当反式GLC由于代谢或其他转运过程而接近于零时，巴比妥酸盐可能会更强地抑制GLUT-1介导的GLC Fluoxin活体。
Barbiturates inhibit GLUT-1 mediated hexose transport bothinvivo[Gjedde & Rasmussen (1980)J. Neurochem.35, 1382−1387; Otsukaet al.(1991)Am. J. Physiol. 261, R265−R275] andin vitro[Honkanenet al.(1995)Biochemistry 34,535−544]. In the present study, the mechanism by which barbiturates inhibit GLUT-1 mediated hexose transport was examined by measuring both unidirectional zero trans and equilibrium exchange fluxes of hexoses in the functionally well-characterized, GLUT-1 rich human erythrocyte system. Unidirectional influx and efflux were both inhibited (>80%) by 10 mM pentobarbital (PB). This symmetrical inhibition of unidirectional flux by PB was virtually independent of cis sugar concentration (2−130 mM) and exhibited an IC50of ∼2 mM. In contrast to unidirectional sugar flux, PB inhibition of equilibrium exchange sugar flux isattenuatedby increased substrate concentration (e.g., 88% inhibition at 1 mM Glc versus 40% inhibition at 130 mM Glc in the presence of 10 mM PB) and exhibits an IC50of ∼10 mM at 100 mM Glc. Other barbiturates were found to inhibit sugar flux in human erythrocytes in this differential manner. These findings, when viewed with kinetic models proposed for GLUT-1 mediated transport [Carruthers (1990)Physiol. Rev. 70,1135−1176], are consistent with barbiturates beingnoncompetitiveinhibitors of Glc translocation and preferentially inhibiting theunoccupiedform of the carrier protein. We propose, therefore, that barbiturates may prevent or alter the conformational changes associated with the reorientation of the carrier protein within the membrane. Overall, these results imply that barbiturates may more strongly inhibit GLUT-1 mediated Glc fluxin vivowhen the trans Glc is near zero as a result of either metabolism or another transport process.