Hoyumpa A M, Strickland R, Sheehan J J, Yarborough G, Nichols S
J Lab Clin Med. 1982 May;99(5):701-8.
The transport of thiamine across the intestine has been characterized in rats but has not been adequately studied in humans. To determine the kinetics of thiamine intestinal transport directly in humans, mucosal tissues were obtained during routine endoscopy from normal-appearing sites at the second portion of the duodenum. With 3H-dextran as the marker of adherent volume, the uptake of 14C-thiamine hydrochloride by the excised mucosa was measured in vitro. By this method thiamine uptake was linear with tissue weight and with incubation time up to 5 min. Results showed that at low thiamine concentrations (0.2 to 2.0 microM), uptake was saturable whereas at high concentrations (5 to 50 microM), uptake was linear with thiamine concentrations. Pyrithiamine, anoxia, N-ethylmaleimide, and replacement of sodium chloride by mannitol reduced the uptake of 0.5 microM thiamine by 42%, 37%, 32% and 35%, respectively (p less than 0.05) but had no effect on the uptake of 20 microM thiamine. These data suggest that, as in the rat, the intestinal transport of thiamine in humans proceeds by a coexistent dual system. At physiologic concentrations, thiamine is transported primarily by an energy-requiring, sodium-dependent active process, whereas at higher pharmacologic concentrations thiamine uptake is predominantly a passive process.
硫胺素在大鼠肠道中的转运已得到研究，但在人类中尚未得到充分研究。为了直接测定硫胺素在人体肠道中的转运动力学，在常规内镜检查时从十二指肠第二部外观正常的部位获取黏膜组织。以3H-葡聚糖作为附着体积的标志物，在体外测量切除黏膜对14C-硫胺素盐酸盐的摄取。通过这种方法，硫胺素摄取与组织重量以及长达5分钟的孵育时间呈线性关系。结果表明，在低硫胺素浓度（0.2至2.0微摩尔）下，摄取是可饱和的，而在高浓度（5至50微摩尔）下，摄取与硫胺素浓度呈线性关系。硫胺素焦磷酸、缺氧、N-乙基马来酰胺以及用甘露醇替代氯化钠分别使0.5微摩尔硫胺素的摄取减少了42%、37%、32%和35%（p小于0.05），但对20微摩尔硫胺素的摄取没有影响。这些数据表明，与大鼠一样，硫胺素在人体肠道中的转运通过共存的双重系统进行。在生理浓度下，硫胺素主要通过需要能量、依赖钠的主动过程转运，而在较高的药理浓度下，硫胺素摄取主要是被动过程。
