The cells of the proximal tubule reabsorb 60-70% of the volume of the filtrate arriving from the glomerulus. Nutrients such as glucose and amino acids are reabsorbed.
Furthermore, different ions are actively reabsorbed by facilitated and co-transport: Na+, K+, Mg2+, SO42-, HCO3-, and PO4-. Water is reabsorbed by osmosis. In the proximal tubule, H+, NH4+, creatinine and drugs are actively secreted into the tubular fluid.
Most of the organic solutes are reabsorbed in the proximal tubule.
What is not true about the function of the proximal tubules?
Extra info: 65% of the filtered sodium is reabsorbed there.