The proximal convoluted tubule (PCT), primarily functions in tubular reabsorption. The PCT reabsorb about 65% of the glomerular filtrate. The concentration of Na⁺ in the tubular fluid is high compared to that in epithelial cells of the PCT. Sodium is thus reabsorbed by both simple diffusion and facilitated diffusion. Sodium carriers will also cotransport glucose and amino acids, thus allowing for the reabsorption of glucose and amino acids. As sodium ions are reabsorbed into the interstitium and then into the blood, an osmotic gradient forms, allowing for the reabsorption of water as well.