Yokota K, Nishi Y, Takesue Y
Biochem Pharmacol. 1983 Nov 15;32(22):3453-7. doi: 10.1016/0006-2952(83)90376-3.
In the present work we studied the effects of phloretin on Na+-dependent D-glucose uptake by brush border membrane vesicles isolated from rabbit small intestine. Phloretin had no inhibitory effect on Na+-dependent D-glucose uptake in the presence of equilibrated Na+, although it inhibited the process in the presence of a Na+ gradient. Phlorizin inhibited Na+-dependent D-glucose uptake both in the presence and in the absence of a Na+ gradient. Phloretin and phlorizin competed with each other for the inhibition of Na+-energized D-glucose uptake. These results indicate that phloretin has no direct interaction with the Na+-dependent D-glucose transporter per se, though phloretin and phlorizin may have a common step(s) in their inhibition mechanisms. Phloretin, but not phlorizin, was found to increase the equilibrium level of D-glucose uptake whether Na+ was present or not. The increase in the equilibrium level was due to phloretin-induced binding of D-glucose to the brush border membrane, but not due to an increase in the intravesicular space. It seems to occur by a mechanism different from that by which phloretin inhibits Na+-energized D-glucose uptake, because the equilibrium level of D-glucose uptake is increased by the ionized form of phloretin but Na+-energized D-glucose uptake is inhibited by the unionized form.
在本研究中，我们研究了根皮素对从兔小肠分离的刷状缘膜囊泡中Na⁺依赖性D - 葡萄糖摄取的影响。在存在平衡的Na⁺的情况下，根皮素对Na⁺依赖性D - 葡萄糖摄取没有抑制作用，尽管它在存在Na⁺梯度的情况下会抑制该过程。根皮苷在存在和不存在Na⁺梯度的情况下均抑制Na⁺依赖性D - 葡萄糖摄取。根皮素和根皮苷在抑制Na⁺驱动的D - 葡萄糖摄取方面相互竞争。这些结果表明，根皮素本身与Na⁺依赖性D - 葡萄糖转运体没有直接相互作用，尽管根皮素和根皮苷在其抑制机制中可能有共同的步骤。发现无论是否存在Na⁺，根皮素而非根皮苷都会增加D - 葡萄糖摄取的平衡水平。平衡水平的增加是由于根皮素诱导的D - 葡萄糖与刷状缘膜的结合，而不是由于囊泡内空间的增加。它似乎是通过一种与根皮素抑制Na⁺驱动的D - 葡萄糖摄取的机制不同的机制发生的，因为D - 葡萄糖摄取的平衡水平是由根皮素的离子化形式增加的，而Na⁺驱动的D - 葡萄糖摄取是由非离子化形式抑制的。
