Toxic Nephropathies: Core Curriculum 2010

Aminoglycoside (AG) antibiotics are filtered freely at the glomerulus. Because of their cationic charge, they are attracted to the proximal tubular apical membrane brush border, which is rich in anionic phospholipids. At this site, they bind the cationic drug receptor megalin (M; encoded by the LRP2 gene) located deep at the base of the brush border villi. The receptor-AG complex is internalized by pinocytosis and taken up by lysosomes (denoted with dotted lines). The adenosine triphosphatase sodium-potassium pump (Na⁺-K⁺-ATPase) is shown at the basolateral surface.

Hydroxyethyl starch (HES) uptake by the apical membrane of proximal tubular cells occurs by pinocytosis. When these pinocytotic vesicles are internalized within the cell, the vesicles fuse with each other and lysosomes. The cytoplasm becomes packed with the lysosomal vacuoles (denoted with HES-containing lysosomes), causing cell swelling and dysfunction. The adenosine triphosphatase sodium-potassium pump (Na⁺-K⁺-ATPase) is shown at the basolateral surface.

Organic anion drugs, such as tenofovir (TDF), are delivered to the basolateral membrane of proximal tubular cells. At this site, they are transported from the blood into the cell by the human organic anion transporter (OAT; encoded by the SLC22A6 gene). When within the cell, they are transported through carrier proteins. Eventually, the organic anion drugs are secreted into the urinary space by apical efflux transporters. In the case of drugs such as tenofovir, multidrug resistance–associated protein (MRP) family members MRP2 and MRP4 (encoded by the ABCC2 and ABCC4 genes, respectively) are the major transporters. Abbreviations: OCT, organic cation transporter; NaDC, sodium dicarboxylate symporter; Pgp, P-glycoprotein.