Vázquez C M, Coleto R, Zanetti R, Ruiz-Gutierrez V
Departamento de Fisiología y Biología Animal, Facultad de Farmacia, C/Tramontana s/n, E-41012 Seville Spain.
Pflugers Arch. 1996 Jun;432(2):329-35. doi: 10.1007/s004240050140.
The current studies explore the effect of hypertension on D-glucose transport into jejunal brush-border membrane vesicles (BBMV). Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, as a control group, were used. The purity of the BBMV from both groups of animals was validated by the finding that the specific activity of brush-border enzyme marker, sucrase, was severalfold greater in membrane vesicles compared with corresponding values in mucosal homogenate. D-glucose uptake was Na+ dependent in both groups of animals, with a transient increase in the intravesicular concentration of D-glucose. However, the initial rate and the magnitude of the accumulation of Na+-dependent D-glucose was significantly higher in SHR compared with WKY rats. In order to investigate the mechanism(s) for the increase in Na+-dependent D-glucose transport in SHR, several experiments were performed: (1) an experiment that indicated 22Na uptake, as an indicator for Na+ permeability, was similar between SHR and WKY rats, (2) kinetic studies that indicated that Vmax values of SHR were significantly greater that those of WKY rats. In contrast, similar Km values for glucose were found between SHR and WKY rats, (3) Na+-dependent phlorizin binding measurements that were not altered by hypertension and (4) a study of the brush-border membrane lipid composition that showed a significant increase in the free cholesterol/phospholipid ratio in SHR. We conclude that altered membrane cholesterol content and consequently altered lipid fluidity could be, at least in part, responsible for the observed increase in Na+-dependent D-glucose transport in SHR.
当前的研究探讨了高血压对D-葡萄糖转运至空肠刷状缘膜囊泡（BBMV）的影响。使用自发性高血压大鼠（SHR）和作为对照组的正常血压Wistar-Kyoto（WKY）大鼠。通过发现刷状缘酶标志物蔗糖酶的比活性在膜囊泡中比在粘膜匀浆中的相应值高几倍，验证了两组动物BBMV的纯度。两组动物中D-葡萄糖的摄取均依赖于Na +，且囊泡内D-葡萄糖浓度有短暂升高。然而，与WKY大鼠相比，SHR中依赖Na +的D-葡萄糖积累的初始速率和幅度明显更高。为了研究SHR中依赖Na +的D-葡萄糖转运增加的机制，进行了几项实验：（1）一项实验表明，作为Na +通透性指标的22Na摄取在SHR和WKY大鼠之间相似；（2）动力学研究表明，SHR的Vmax值明显高于WKY大鼠。相反，SHR和WKY大鼠之间发现葡萄糖的Km值相似；（3）依赖Na +的根皮苷结合测量未因高血压而改变；（4）一项对刷状缘膜脂质组成的研究表明，SHR中游离胆固醇/磷脂比率显著增加。我们得出结论，膜胆固醇含量的改变以及由此导致的脂质流动性改变可能至少部分地导致了SHR中观察到的依赖Na +的D-葡萄糖转运增加。
