Turnbull A J, Blakeborough P, Thompson R P
Gastrointestinal Laboratory, Rayne Institute, St Thomas' Hospital, London.
Br J Nutr. 1990 Nov;64(3):733-41. doi: 10.1079/bjn19900075.
Intestinal brush-border-membrane vesicles were prepared from the porcine small bowel by magnesium precipitation and differential centrifugation, and were functionally intact. The influence of dietary ligands on 65Zn uptake was determined using a 65Zn concentration of 5 microM, an incubation time of 1 min and a reaction temperature of 27 degrees, with a rapid filtration technique. At this low Zn concentration the addition of an excess of folate, histidine or glucose had no effect on Zn uptake. Addition of picolinate, citrate and phytate to the incubation medium significantly reduced Zn uptake at all concentrations of ligand examined. Any inhibitory effects of folic acid in vivo may thus be due to a mucosal rather than lumen interaction. Those ligands inhibiting absorption may have done so through the formation of Zn-ligand complexes, which are either insoluble, or which reduce the binding of Zn to its mucosal receptor. This in vitro model of Zn absorption is useful for comparing the effects of potential Zn-binding ligands in the diet.
通过镁沉淀和差速离心法从猪小肠制备了肠刷状缘膜囊泡，其功能完整。采用快速过滤技术，在65Zn浓度为5微摩尔、孵育时间为1分钟、反应温度为27摄氏度的条件下，测定膳食配体对65Zn摄取的影响。在这种低锌浓度下，添加过量的叶酸、组氨酸或葡萄糖对锌摄取没有影响。在所有检测的配体浓度下，向孵育培养基中添加吡啶甲酸、柠檬酸盐和肌醇六磷酸均显著降低锌摄取。因此，叶酸在体内的任何抑制作用可能是由于黏膜而非管腔相互作用。那些抑制吸收的配体可能是通过形成锌-配体复合物来实现的，这些复合物要么不溶，要么减少锌与其黏膜受体的结合。这种锌吸收的体外模型有助于比较饮食中潜在锌结合配体的作用。
