Stein J, Schröder O, Milovic V, Caspary W F
Second Department of Internal Medicine, Johann Wolfgang Goethe University, Frankfurt, Germany.
Gastroenterology. 1995 Mar;108(3):673-9. doi: 10.1016/0016-5085(95)90438-7.
BACKGROUND/AIMS: Previous observations have shown that mercapto- and bromo- short-chain fatty acids diminish fatty acid use in colonic epithelium. The aim of this study was to investigate whether this effect is attributable to the inhibition of short-chain fatty acid uptake.
Apical membrane vesicles of rat colonocytes were prepared by a discontinuous sucrose gradient after isolation of membrane caps. [14C]butyrate uptake was measured by rapid filtration technique.
Preloading of isolated apical membrane vesicles with bicarbonate or butyrate stimulated [14C]butyrate uptake and resulted in up to fivefold overshoots. Increasing extravesicular butyrate concentrations saturated the bicarbonate-stimulated butyrate uptake with a binding constant of 44.7 +/- 5.9 mmol/L and a maximum velocity of 33.2 +/- 2.7 nmol.mg protein-1.3 s-1. Intravesicular butyrate uptake was inhibited by addition of 20 mmol/L 3-mercaptopropionate (43.0% +/- 5.6%), whereas 2-bromo-propionate (13.9% +/- 4.1%) and 4-bromobutyrate (22.6% +/- 5.3%) did not significantly alter butyrate uptake. Increasing concentrations of 3-mercaptopropionate had a competitive inhibitory effect on butyrate uptake with a binding constant following inhibition of 6.25 +/- 0.87 mmol/L and a maximum velocity of 5.82 +/- 1.01 nmol.mg protein-1.3 s-1.
Butyrate uptake in apical membrane vesicles of rat distal colon is mediated by a low-affinity anion transport system, which can be competitively inhibited by 3-mercaptopropionate but not by 2-bromopropionate and 4-bromobutyrate.
背景/目的：先前的观察表明，巯基和溴代短链脂肪酸会减少结肠上皮细胞中脂肪酸的利用。本研究的目的是调查这种效应是否归因于短链脂肪酸摄取的抑制。
在分离膜帽后，通过不连续蔗糖梯度制备大鼠结肠上皮细胞的顶端膜囊泡。采用快速过滤技术测量[14C]丁酸的摄取。
用碳酸氢盐或丁酸预加载分离的顶端膜囊泡可刺激[14C]丁酸的摄取，并导致高达五倍的过冲。增加囊泡外丁酸浓度可使碳酸氢盐刺激的丁酸摄取饱和，结合常数为44.7±5.9 mmol/L，最大速度为33.2±2.7 nmol·mg蛋白-1·3 s-1。加入20 mmol/L 3-巯基丙酸可抑制囊泡内丁酸的摄取（43.0%±5.6%），而2-溴丙酸（13.9%±4.1%）和4-溴丁酸（22.6%±5.3%）对丁酸摄取没有显著影响。增加3-巯基丙酸的浓度对丁酸摄取具有竞争性抑制作用，抑制后的结合常数为6.25±0.87 mmol/L，最大速度为5.82±1.01 nmol·mg蛋白-1·3 s-1。
大鼠远端结肠顶端膜囊泡中丁酸的摄取由低亲和力阴离子转运系统介导，该系统可被3-巯基丙酸竞争性抑制，但不受2-溴丙酸和4-溴丁酸的影响。
