Under what conditions will the kidney produce concentrated urine? If: A. glomerular fi ltration rate is low. B. glomerular fi ltration rate is high. C. atrial natriuretic peptide and aldosterone are present in blood. D. antidiuretic hormone and aldosterone are present in the blood.
Option D. Aldosterone causes sodium to be absorbed from the filterate at the DCT and collecting duct. This units up an osmotic gradient. ADH makes the tubule extra permeable to water. Hence water can circulate from the filterate into the tubule cells alongside the osmotic gradient.
