Forsyth G W, Gabriel S E
Veterinary Physiological Sciences, University of Saskatchewan, Saskatoon, Canada.
Biochim Biophys Acta. 1989 Oct 26;977(1):19-25. doi: 10.1016/s0005-2728(89)80004-0.
alpha-Phenylcinnamate has been investigated in comparison to other inhibitors of chloride ion transport into porcine jejunal brush-border membrane vesicles. The transport modes studied included uptake driven only by a chemical Cl gradient, Cl uptake dependent on a transmembrane potential, self-exchange of Cl with no chemical or potential gradient, and Cl uptake dependent on a chemical gradient for bicarbonate. Uptake driven by the chemical gradient for Cl was strongly inhibited by millimolar concentrations of diphenylamine-2-carboxylate, 5-nitro-2-(2-phenylethylamino)benzoate (NPEB), and to a lesser extent by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS). Similar concentrations of alpha-phenylcinnamate did not reduce this mode of Cl uptake. Conductive Cl uptake driven by a potassium gradient was inhibited by approx. 50% at 2.5 mM alpha-phenylcinnamate. alpha-Phenylcinnamate was equally effective in reducing the initial rate of conductive chloride accumulation in vesicles with naturally opened Cl channels (conductance activation by cyclic AMP and Ca2+), or with Cl channels opened by exposure to tetramethylammonium (TMA) buffer. In comparison with diphenylamine-2-carboxylate, NPEB and SITS, alpha-phenylcinnamate had the least effect on Cl-HCO3 exchange at inhibitor concentrations which reduced conductance activity. Self-exchange rates of physiological concentrations of Cl were also relatively unaffected by low mM concentrations of alpha-phenylcinnamate. Kinetic analysis indicated that alpha-phenylcinnamate was an uncompetitive inhibitor, requiring the presence of the normal Cl ligand for binding to, and inhibition of, conductive Cl transport by pig intestinal brush-border vesicles.
已将α-苯基肉桂酸酯与其他氯离子转运至猪空肠刷状缘膜囊泡的抑制剂进行了比较研究。所研究的转运模式包括仅由化学氯离子梯度驱动的摄取、依赖跨膜电位的氯离子摄取、无化学或电位梯度的氯离子自交换以及依赖碳酸氢根化学梯度的氯离子摄取。由氯离子化学梯度驱动的摄取受到毫摩尔浓度的二苯胺-2-羧酸盐、5-硝基-2-(2-苯乙氨基)苯甲酸盐（NPEB）的强烈抑制，4-乙酰氨基-4'-异硫氰基芪-2,2'-二磺酸盐（SITS）的抑制作用较小。类似浓度的α-苯基肉桂酸酯并未降低这种氯离子摄取模式。由钾离子梯度驱动的氯离子传导性摄取在2.5 mMα-苯基肉桂酸酯时受到约50%的抑制。α-苯基肉桂酸酯在降低具有自然开放氯离子通道（由环磷酸腺苷和钙离子激活电导）或通过暴露于四甲基铵（TMA）缓冲液而开放氯离子通道的囊泡中氯离子传导性积累的初始速率方面同样有效。与二苯胺-2-羧酸盐、NPEB和SITS相比，在降低电导活性的抑制剂浓度下，α-苯基肉桂酸酯对氯离子-碳酸氢根交换的影响最小。生理浓度氯离子的自交换速率也相对不受低毫摩尔浓度α-苯基肉桂酸酯的影响。动力学分析表明，α-苯基肉桂酸酯是一种非竞争性抑制剂，需要正常氯离子配体的存在才能与猪肠刷状缘囊泡结合并抑制氯离子传导性转运。
