Selective reabsorption takes place in the proximal convoluted tubule. 85% of the filtrate is reabsorbed. Sodium-potassium pumps actively transport Na+ ions out of the epithelial cells on the capillary side. This creates a low Na+ concentration inside the cell. The cell surface membrane in contact with the filtrate has many microvilli and co-transporter proteins that transport Na+ associated with glucose or amino-acids from the lumen into the epithelial cells by facilitated diffusion. Once in the cell the glucose/amino-acids diffuse into the blood down their concentration gradient and are also actively transported. Water follows by osmosis.