(2) Compared with plasma, the fluid in renal capsule contains less protein, including water, glucose, inorganic salts and urea. This shows that the glomerular and renal capsule wall can penetrate water, glucose, inorganic salts, urea and other small molecules, but rarely penetrate protein and other substances.
(3) This shows that renal tubules can reabsorb all glucose in renal sac fluid.