When insulin acts on human muscle cells, it turns on a switch (ERK1/2) that helps modify a specific protein (the sodium-potassium pump) at certain spots—this has been seen in lab tests using drugs and purified enzymes.

Insulin helps move certain proteins to the surface of human muscle cells and boosts their activity, and this seems to involve a specific cellular signaling process.

When a certain protein in human muscle cells is blocked, insulin can't turn on or move a key cellular pump that helps muscles work properly.

When you eat, your body releases insulin, which helps muscle cells pull more potassium from your blood by putting more pumps on their surface—this keeps your muscles working smoothly after meals.

When insulin is present in rat muscle cells, it makes a special pump work harder to move salt in and out of the cells—but if you block certain cleanup enzymes in the cell, the pump doesn’t speed up anymore, which suggests insulin uses those enzymes to turn the pump on.

When rats are given insulin, a specific part of a pump in their muscle cells moves from inside the cell to the outer membrane, but another similar part stays where it is.