Where is P-glycoprotein located on GI tract cells?

Where is P-glycoprotein located on GI tract cells?

• A. Basolateral membrane
• B. Apical membrane
• C. Nuclear membrane
• D. Mitochondrial membrane

Answer: (B)

P-glycoprotein acts as an energy-dependent efflux transporter located on the apical (luminal) surface of intestinal epithelial cells. This placement faces the gut lumen, so it can pump substrates back into the intestinal cavity as they try to cross the cell, reducing absorption and contributing to oral drug efflux. That makes the apical membrane the correct location. The nuclear and mitochondrial membranes are not typical sites for P-gp, and while other tissues may have different orientations, in the GI tract the key barrier function is achieved at the apical surface, facing the lumen.

P-glycoprotein acts as an energy-dependent efflux transporter located on the apical (luminal) surface of intestinal epithelial cells. This placement faces the gut lumen, so it can pump substrates back into the intestinal cavity as they try to cross the cell, reducing absorption and contributing to oral drug efflux. That makes the apical membrane the correct location. The nuclear and mitochondrial membranes are not typical sites for P-gp, and while other tissues may have different orientations, in the GI tract the key barrier function is achieved at the apical surface, facing the lumen.