Carroll K M, Wood R J, Chang E B, Rosenberg I H
Department of Medicine, University of Chicago, Illinois 60637.
Am J Physiol. 1988 Sep;255(3 Pt 1):G339-45. doi: 10.1152/ajpgi.1988.255.3.G339.
Glucose stimulates calcium transport in vitro in rat duodenal tissue and isolated enterocytes. Under short-circuited conditions, glucose increased mucosal to serosal calcium flux (JCa(m----s)) without altering serosal to mucosal calcium flux (JCa(s----m)) in the duodenum, the primary site of active calcium absorption in the rat small intestine. The half-maximal dose (ED50) of the glucose stimulatory effect was less than 1 mM, and an increase in JCa(m----s) of 80% over control was seen at a glucose concentration of 50 mM. Glucose did not increase calcium flux in the ileum where active calcium absorption is minimal. Glucose stimulated net calcium uptake by 35% in isolated duodenal enterocytes. Glucose did not alter calcium efflux from preloaded enterocytes suspended in calcium-free buffer. Glucose enhancement of net calcium uptake in enterocytes was not caused by altered cell membrane integrity or functional viability. The nonmetabolizable glucose analogue alpha-methylglucoside did not stimulate calcium transport. Our findings suggest that glucose can stimulate intestinal calcium absorption, at least partially, by enhancing transcellular calcium transport and that cellular glucose metabolism is necessary for stimulation of this route of calcium transport.
葡萄糖在体外可刺激大鼠十二指肠组织和分离的肠细胞中的钙转运。在短路条件下，葡萄糖增加了十二指肠黏膜到浆膜的钙通量（JCa(m----s)），而未改变十二指肠浆膜到黏膜的钙通量（JCa(s----m)），十二指肠是大鼠小肠中钙主动吸收的主要部位。葡萄糖刺激作用的半数有效剂量（ED50）小于1 mM，在葡萄糖浓度为50 mM时，JCa(m----s)比对照组增加了80%。葡萄糖在回肠（钙主动吸收极少）中并未增加钙通量。葡萄糖使分离的十二指肠肠细胞的净钙摄取增加了35%。葡萄糖并未改变悬浮于无钙缓冲液中的预先加载钙的肠细胞的钙外流。葡萄糖对肠细胞净钙摄取的增强并非由细胞膜完整性或功能活力的改变所致。不可代谢的葡萄糖类似物α-甲基葡萄糖苷不会刺激钙转运。我们的研究结果表明，葡萄糖至少可部分通过增强跨细胞钙转运来刺激肠道钙吸收，并且细胞葡萄糖代谢对于刺激这条钙转运途径是必需的。
