What is the function of P-glycoprotein across the following organs: intestine, liver, kidney, and brain?

What is the function of P-glycoprotein across the following organs: intestine, liver, kidney, and brain?

• A. Intestine: prevent absorption; Liver: excretion into bile; Kidney: excretion into urine; Brain: prevent entry from blood into brain
• B. Intestine: promote absorption; Liver: excretion into bile; Kidney: excretion into urine; Brain: prevent entry from blood into brain
• C. Intestine: prevent absorption; Liver: excretion into urine; Kidney: excretion into bile; Brain: prevent entry from blood into brain
• D. Intestine: promote absorption; Liver: excretion into urine; Kidney: prevent entry into brain; Brain: promote entry

Answer: (A)

P-glycoprotein acts as an ATP-dependent efflux transporter that pumps its substrates out of cells. This makes it a key defender against drug absorption and distribution: it limits oral bioavailability, promotes excretion, and protects sensitive sites like the brain. In the intestine, P-glycoprotein sits on the apical (lumen-facing) membrane of enterocytes and actively pumps absorbed drug back into the intestinal lumen, thereby preventing or reducing absorption. In the liver, it is located on the canalicular membrane of hepatocytes and pumps drugs into bile for biliary excretion. In the kidney, P-glycoprotein on the apical membrane of proximal tubule cells moves drugs into the urine, aiding renal excretion. At the blood–brain barrier, P-glycoprotein on the luminal side of brain capillary endothelial cells pumps substrates back into the bloodstream, hindering entry into the brain. This pattern matches the option describing intestine to reduce absorption, liver to excrete into bile, kidney to excrete into urine, and brain to prevent entry from blood into the brain.

P-glycoprotein acts as an ATP-dependent efflux transporter that pumps its substrates out of cells. This makes it a key defender against drug absorption and distribution: it limits oral bioavailability, promotes excretion, and protects sensitive sites like the brain.

In the intestine, P-glycoprotein sits on the apical (lumen-facing) membrane of enterocytes and actively pumps absorbed drug back into the intestinal lumen, thereby preventing or reducing absorption. In the liver, it is located on the canalicular membrane of hepatocytes and pumps drugs into bile for biliary excretion. In the kidney, P-glycoprotein on the apical membrane of proximal tubule cells moves drugs into the urine, aiding renal excretion. At the blood–brain barrier, P-glycoprotein on the luminal side of brain capillary endothelial cells pumps substrates back into the bloodstream, hindering entry into the brain.

This pattern matches the option describing intestine to reduce absorption, liver to excrete into bile, kidney to excrete into urine, and brain to prevent entry from blood into the brain.