GLUT4 is the insulin-regulated glucose transporter found primarily in adipose tissues and striated muscle (skeletal and cardiac) that is responsible for insulin-regulated glucose transport into the cell. Under conditions of low insulin, GLUT4 is sequestered in intracellular vesicles in muscle and fat cells. Insulin induces a rapid increase in the uptake of glucose by inducing the translocation of GLUT4 from these vesicles to the plasma membrane. Muscle contraction stimulates muscle cells to translocate GLUT4 receptors to their surfaces. This is especially true in cardiac muscle, where continuous contraction can be relied upon; but is observed to a lesser extent in skeletal muscle.
