At the End of the Proximal Tubule, Tubule Fluid Osmolarity

Question

At the end of the proximal tubule, tubule fluid osmolarity is about
A) 600 mOsM
B) 300 mOsM
C) 100 mOsM
D) 70 mOsM
E) 1200 mOsM

Accepted Answer

At the end of the proximal tubule, the tubule fluid osmolarity is approximately 300 mOsM, which is isotonic to plasma. This is because the proximal tubule reabsorbs water and solutes at roughly equal rates, maintaining isotonicity with plasma.