Question

If a child were born with a mutation that made the ascending limb of the loop of henle permeable to water, what would be the minimum and maximum urine osmolarities the child could produce? units are in mosm.
a. minimum 100 / maximum 300
b. minimum 300 / maximum 1200
c. minimum 100 / maximum 100
d. minimum 100 / maximum 1200
e. minimum 300 / maximum 300

Answer 1

In normal situations:
-The thin ascending limb is of the loop of henle is impermeable to water. But, is permeable to ions (sodium, chloride) that cross by diffusion.
-Urine osmolality should be 300-900 mOsm/kg of water.

In this case, if the ascending limb of the loop of henle is permeable to water is the same as saying the loop isn't doing it's job of creating a concentration gradient.
Because of that, The process  of reabsorption of water and creation of a concentrated urine is not correctly happening.

The answer is E. minimum 300 / maximum 300

The loop of Henle receives isotonic (300 mOsm/L) fluid, from the proximal convoluted tubule, and since it's not working th way it should it won't change those values.