In which part of the kidney does Angiotensin II cause water reabsorption?

Angiotensin II primarily acts on the collecting duct to promote water reabsorption. This hormone enhances the reabsorption of sodium through its effect on the epithelial cells of the collecting duct, leading to an increase in water reabsorption due to osmotic forces created by sodium retention. In the presence of Angiotensin II, the collecting duct becomes more permeable to water, largely influenced by the action of antidiuretic hormone (ADH), which is also enhanced by Angiotensin II. This mechanism is crucial for regulating blood pressure and fluid balance in the body.

In contrast, while the proximal convoluted tubule is a significant site for sodium and water reabsorption, the primary regulatory role of Angiotensin II is more pronounced in the collecting duct. The loop of Henle and distal convoluted tubule also contribute to water and electrolyte balance, but Angiotensin II’s primary influence relevant to the question lies in the collecting duct's role in fine-tuning water reabsorption, particularly during states of fluid deficiency or low blood volume.