ADH or vasopressin facilitates water reabsorption from latter parts of the tubule. Large amounts of water could be reabsorbed from the collecting duct to produce a concentrated urine.
An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release. Therefore, when we drink lots of water, ADH release decreases.
A fall in glomerular blood flow/glomerular blood pressure/ GFR can activate the JG cells to release renin which converts angiotensinogen in blood to angiotensin I and further to angiotensin II.

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