Question

A person who is unable to synthesize vasopressin?

Select one:

a. Is unable to reabsorb water in the proximal tubule

b. Is diabetic and will excrete glucose in the urine

c. Will excrete a very dilute urine

d. Will excrete approximately 180 L of urine per day because they cannot reabsorb water after it is filtered

e. None of the above are correct

Answer 1

The correct answer is option c

Concentration of urine takes place in the presence of hormone vasopressin(ADH).ADH increases the water reabsorption in the DCT and CD of kidneys.As the person is unable to synthesize vasopressin, water reabsorption decreases and concentrated urine is not produced.Thus excreting very dilute urine.

Role of ADH is mainly at CD and DCT.It has minimal or no role in reabsorption of water at PCT.

Diabetus insipidus is a condition due to decreased Vasopressin levels.The person with diabetes insipidus excretes large amounts of urine but the glucose levels remain the same.

In the human body about 180 litre of filtrate is produced per day.About 99% of it is reabsorbed.Thus the urine produced would be around 1.5 litre per day.Even if the vasopressin levels fall to low levels,there is no such large excretion of about 180 litres of urine.Most of it will be reabsorbed.The urinary excretion increases but not to a very high extent.