Simpson I B, Karnieli E, Hissin P J, Smith U, Cushman S W
Soc Gen Physiol Ser. 1985;39:43-55.
The mechanism by which insulin stimulates glucose transport in the rat adipose cell has been shown to be a rapid, reversible, and energy-dependent process. Stimulation is achieved by the translocation of glucose transporters from an intracellular pool to the plasma membrane where their insertion is ultimately responsible for the increase in transport activity. The reversal of this process also occurs rapidly at 37 degrees C, with the transporters reappearing in the intracellular pool. The overall cycle thus appears as a reversible endocytic-exocytic process with the endocytic and exocytic steps showing markedly different kinetic properties. Studies of the effects of incubation temperature and TRIS confirm the existence of an intermediate state in which transporters are associated with the plasma membrane but incapable of transporting extracellular glucose. This suggests that insulin may act at the level of the plasma membrane at the step that results in the exposure of functional glucose transporters. The existence of a cAMP-mediated process capable of overriding the actions of insulin raises the possibility of a second level of control of glucose transport activity the significance of which remains to be assessed. Finally, a third control mechanism exists for regulating the absolute number of glucose transporters per cell that appears to be specifically affected in certain pathophysiological conditions in the rat.
胰岛素刺激大鼠脂肪细胞葡萄糖转运的机制已被证明是一个快速、可逆且依赖能量的过程。刺激是通过葡萄糖转运体从细胞内池转运到质膜来实现的，转运体在质膜上的插入最终导致转运活性增加。在37摄氏度时，这个过程的逆转也会迅速发生，转运体重新出现在细胞内池中。因此，整个循环表现为一个可逆的内吞-外排过程，内吞和外排步骤表现出明显不同的动力学特性。对孵育温度和三羟甲基氨基甲烷（TRIS）作用的研究证实了存在一种中间状态，即转运体与质膜相关但无法转运细胞外葡萄糖。这表明胰岛素可能在导致功能性葡萄糖转运体暴露的步骤中作用于质膜水平。一种能够超越胰岛素作用的环磷酸腺苷（cAMP）介导过程的存在，增加了对葡萄糖转运活性进行二级控制的可能性，其意义仍有待评估。最后，存在第三种控制机制来调节每个细胞中葡萄糖转运体的绝对数量，在大鼠的某些病理生理条件下，这种机制似乎会受到特异性影响。
