Behnke RD, Busquets-Turner L, Ahearn GA
Department of Zoology, University of Hawaii, Honolulu, HI 96822, USA.
J Exp Biol. 1998 Dec;201 (Pt 24):3385-93. doi: 10.1242/jeb.201.24.3385.
Transport of d-[3H]glucose into lobster (Homarus americanus) brush-border membrane vesicles (BBMVs) prepared by Mg2+ precipitation from antennal gland labyrinth-coelomosac tissue was examined. Influx of d-glucose occurred primarily by a phlorizin-sensitive, Na+-dependent carrier similar to that found in vertebrate renal epithelium. An inwardly directed Na+ gradient drove concentrative d-glucose uptake, whereas similar gradients of Li+ and K+ did not. Stimulation by the Na+ gradient was further enhanced by the imposition of an inside-negative potential difference and also by increases in the pH of the vesicle and incubation media. An analysis of cis inhibition of d-glucose uptake by a number of sugars and sugar derivatives indicated that the transporter requires (a) that the sugar substrate be a d-pyranose in the C1 chair conformation and (b) that the hydroxyl groups at C2 and C3 of the ring be unmodified and equatorial. Apparent kinetic parameters for glucose uptake were determined under zero-trans, short-circuited conditions. Maximal influx of d-glucose into vesicles was estimated to be 96 pmol mg-1 protein s-1. Half-maximal influx was determined to occur at 0.20 mmol l-1 d-glucose. The relationship between external Na+ concentration and glucose influx was sigmoidal, and the stoichiometry of Na+-dependent glucose transport found to be 3 Na+:1 glucose using the static head method.
研究了通过镁离子沉淀法从触角腺迷路 - 体腔囊组织制备的龙虾（美洲螯龙虾）刷状缘膜囊泡（BBMVs）对d-[³H]葡萄糖的转运。d-葡萄糖的内流主要通过一种对根皮苷敏感、依赖钠离子的载体进行，类似于在脊椎动物肾上皮中发现的载体。内向的钠离子梯度驱动了d-葡萄糖的浓缩摄取，而类似的锂离子和钾离子梯度则不能。钠离子梯度的刺激作用通过施加内膜负电位差以及增加囊泡和孵育介质的pH值而进一步增强。对多种糖类和糖衍生物对d-葡萄糖摄取的顺式抑制作用的分析表明，转运体要求：（a）糖底物为处于C1椅式构象的d-吡喃糖；（b）环上C2和C3位的羟基未被修饰且处于平伏键位置。在零转运、短路条件下测定了葡萄糖摄取的表观动力学参数。估计d-葡萄糖进入囊泡的最大内流速率为96 pmol mg⁻¹蛋白质 s⁻¹。半最大内流速率测定为在0.20 mmol l⁻¹ d-葡萄糖时出现。外部钠离子浓度与葡萄糖内流之间的关系呈S形，使用静态水头法发现钠离子依赖的葡萄糖转运化学计量比为3 Na⁺:1葡萄糖。
