SODIUM-POTASSIUM ATPase PUMP

QUESTION:
The mechanism for active transfer of sodium out of the cell and potassium into the cell (select all that apply) :
1. is referred to as the sodium-potassium pump
2. requires no energy, being a passive movement
3. is located in the cell membrane
4. functions independent of the sodium concentration

ANSWER:
1 & 3.  Sodium transport via the sodium-potassium pump is a process that requires energy.  The pump is in the cell membrane.  The process is related to the sodium concentration, since sodium is the rate-limiting step.



The Na-K ATPase Pump (phew!) is a protein found in all cells which keeps intracellular K high, and intracellular Na low.  This pump uses energy derived from the breakdown of ATP to go through a series of shape changes (conformational change) to ultimately move 3 sodium ions out of the cell in exchange for 2 potassium ions in.

CLINICAL APPLICATION:

*Hyperkalemia treatments:

• Insulin stimulates the Na-K pump to drive K+ into the cells making it an effective agent for hyperkalemia.  Insulin also opens glucose channels (permits transfer of glucose into fat and skeletal muscle cells).  The glucose component of the glucose-insulin therapy for hyperkalemia prevents hypoglycemia.
• 10 units insulin
• 12.5-25 gm D50W
• B2 adrenergic agonists also stimulates the Na-K pump to drive K+ into cells.
• albuterol

*Side effects of B2 Adrenergic Agonist drugs is hypokalemia:

• Terbutaline & ritodrine cause hypokalemia.
• These drugs are tocolytics - used to delay preterm labor for 48 hrs to allow fetal lung maturity with steroids.
• Ritodrine is no longer used.

References: Valley Anesthesia