The exofacial GLUT4 antibody LM048 specifically detects GLUT4 translocation to the sarcolemma in human and rodent muscle without labeling intracellular GLUT4 pools, while the antibody LM059 detects both sarcolemmal and intracellular GLUT4, enabling differentiation of GLUT4 translocation states.

When muscle needs more glucose, either insulin or exercise signals the cell to move glucose transporters from inside the cell to the outer surface. These transporters are carried in tiny sacs that fuse with the cell membrane, exposing them to the outside. Once on the surface, they pull glucose into the muscle. One antibody can only see the transporters on the surface, while another sees both surface and inside transporters, allowing scientists to tell when movement has happened.