Moran A, Turner R J, Handler J S
J Biol Chem. 1983 Dec 25;258(24):15087-90.
Cultured porcine kidney cells (LLC-PK1) form polarized epithelia that transport glucose from apical to basal surface as in the renal proximal tube. The ability of these cells to transport glucose is known to increase as the epithelium forms and matures in culture. We find that epithelia grown in medium containing 25 mM glucose have reduced hexose transport compared to epithelia grown in 5 mM glucose. This difference is not the result of differences in seeding efficiency and can be reversed by changing the concentration of glucose in the growth medium. Increased transport in epithelia grown in 5 mM glucose is the result of increased influx on the sodium-coupled apical membrane transporter rather than changes in efflux. This difference is apparently the result of more apical membrane transporters in epithelia grown in 5 mM glucose. The number of high affinity phlorizin-binding sites is greater in epithelia grown in 5 mM glucose (about 0.8 pmol/10(6) cells) than in 25 mM glucose (about 0.25 pmol/10(6) cells). The increase in the number of glucose transporters induced by the low glucose medium is specific in that there is not a comparable change in activity of marker enzymes (alkaline phosphatase, acid phosphatase, or glucose 6-phosphatase). The nature of the intracellular signal elicited by extracellular glucose remains to be determined.
培养的猪肾细胞（LLC-PK1）形成极化上皮细胞，其从顶端向基底表面转运葡萄糖，就像在肾近端小管中一样。已知这些细胞转运葡萄糖的能力会随着上皮细胞在培养中形成和成熟而增强。我们发现，与在5 mM葡萄糖中生长的上皮细胞相比，在含有25 mM葡萄糖的培养基中生长的上皮细胞己糖转运减少。这种差异不是接种效率差异的结果，并且可以通过改变生长培养基中葡萄糖的浓度来逆转。在5 mM葡萄糖中生长的上皮细胞转运增加是钠偶联顶端膜转运体流入增加的结果，而不是流出变化的结果。这种差异显然是由于在5 mM葡萄糖中生长的上皮细胞中顶端膜转运体更多。在5 mM葡萄糖中生长的上皮细胞中高亲和力根皮素结合位点的数量（约0.8 pmol/10(6)个细胞）比在25 mM葡萄糖中生长的上皮细胞（约0.25 pmol/10(6)个细胞）更多。低葡萄糖培养基诱导的葡萄糖转运体数量增加具有特异性，因为标记酶（碱性磷酸酶、酸性磷酸酶或葡萄糖6-磷酸酶）的活性没有可比变化。细胞外葡萄糖引发的细胞内信号的性质仍有待确定。
