Tomimatsu T, Horie T
Laboratory of Biopharmaceutics, Faculty of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
In Vivo. 2001 Jan-Feb;15(1):81-6.
The administration of retinyl palmitate (RP) to rats enhanced Na(+)-dependent D-glucose transport in the small intestine. Effects of RP on Na(+)-dependent D-glucose cotransporter (SGLT1) in rat small intestine were investigated in this study. RP was orally administered (1000 IU/kg/day) to rats for 3 days. The uptake of [3H]D-glucose into the brush-border membrane vesicles (BBMV) of the RP-treated rats, was 1.7-fold larger than that of the control rats. The western blot analysis of SGLT1 protein in BBMV indicated that the amount of SGLT1 was unaffected by the RP treatment. Scatchard analysis of phlorizin binding to both BBMV also showed that the dissociation constant (Kd) and number of phlorizin binding site (Bmax) were unchanged by the RP treatment. The fluidity of the brush-border membrane (BBM) was examined by measuring the fluorescence anisotropy of BBM labeled with 1, 6-diphenyl-1, 3, 5-hexatriene (DPH). The membrane fluidity decreased in the RP-treated rats compared with that of the control rats. In conclusion, the RP treatment increased the glucose transport in BBMV. This enhancement of glucose transport is unlikely due to the change in the amount of SGLT1 protein in BBM. The decrease of the BBM fluidity may contribute to the enhancement of glucose transport in BBM of the RP-treated rats by changing the affinity of SGLT1 for glucose and/or the turnover rate of SGLT1.
给大鼠施用视黄醇棕榈酸酯（RP）可增强小肠中钠依赖性D-葡萄糖转运。本研究调查了RP对大鼠小肠中钠依赖性D-葡萄糖共转运蛋白（SGLT1）的影响。以1000 IU/kg/天的剂量给大鼠口服RP，持续3天。RP处理组大鼠刷状缘膜囊泡（BBMV）对[3H]D-葡萄糖的摄取量是对照组大鼠的1.7倍。对BBMV中SGLT1蛋白进行的蛋白质免疫印迹分析表明，RP处理对SGLT1的量没有影响。对二者BBMV中根皮素结合进行的Scatchard分析也表明，RP处理后根皮素的解离常数（Kd）和结合位点数量（Bmax）没有变化。通过测量用1,6-二苯基-1,3,5-己三烯（DPH）标记的BBM的荧光各向异性来检测刷状缘膜（BBM）的流动性。与对照组大鼠相比，RP处理组大鼠的膜流动性降低。总之，RP处理增加了BBMV中的葡萄糖转运。这种葡萄糖转运的增强不太可能是由于BBM中SGLT1蛋白量的变化所致。BBM流动性的降低可能通过改变SGLT1对葡萄糖的亲和力和/或SGLT1的周转率，导致RP处理组大鼠BBM中葡萄糖转运增强。
