Two mechanisms by which P-glycoprotein activity can be increased are:

Two mechanisms by which P-glycoprotein activity can be increased are:

• A. Increase amount of P-glycoprotein in cells; Increase intrinsic activity of the same number of P-glycoprotein.
• B. Increase amount of P-glycoprotein; Decrease intrinsic activity.
• C. Decrease P-glycoprotein expression.
• D. Inhibit P-glycoprotein ATPase activity.

Answer: (A)

P-glycoprotein activity can rise by two separate routes: more transporter molecules present in the cell, and each transporter working more efficiently. The total efflux capacity depends on both how many pumps you have and how fast each pump can move substrates. So increasing the number of P-glycoprotein molecules in cells increases the overall activity, and if, in addition, you boost the intrinsic activity of the same number of pumps (making each pump work faster), the combined effect further raises activity. That’s why the best answer combines both: more P-glycoprotein plus higher intrinsic activity of those pumps. Increasing amount alone is beneficial, but if intrinsic activity were reduced, or if P-glycoprotein expression were decreased, overall activity would drop. Inhibiting ATPase activity would deprive the pumps of the energy needed to transport substrates, reducing activity rather than increasing it.

P-glycoprotein activity can rise by two separate routes: more transporter molecules present in the cell, and each transporter working more efficiently. The total efflux capacity depends on both how many pumps you have and how fast each pump can move substrates. So increasing the number of P-glycoprotein molecules in cells increases the overall activity, and if, in addition, you boost the intrinsic activity of the same number of pumps (making each pump work faster), the combined effect further raises activity. That’s why the best answer combines both: more P-glycoprotein plus higher intrinsic activity of those pumps.

Increasing amount alone is beneficial, but if intrinsic activity were reduced, or if P-glycoprotein expression were decreased, overall activity would drop. Inhibiting ATPase activity would deprive the pumps of the energy needed to transport substrates, reducing activity rather than increasing it.