The highest percentage of glomerular filtrate reabsorption occurs in:

Under all circumstances most of the filtrate is reabsorbed in the proximal tubule. Normally, this reabsorption amounts to about two-thirds of the sodium and water filtered. Normally 60% of Na+ is reabsorbed in the proximal tubule, primarily by Na-H exchange. Ref: Ganong's review of Medical Physiology, 23rd Ed, page 648-650