The water potential of blood rises. This is detected by osmoreceptors in the hypothalamus in the brain. This detection stimulates less ADH to be released. ADH is Antidiuretic Hormone. It’s role is to alter membrane permeability in the collecting ducts of the kidney’s nephrons. (It is produced by the hypothalamus but stored in the posterior pituitary gland)less ADH = less permeable collecting duct membranes. Water therefore remains within the nephron and collected in the urine. Aquaporin channels are temporarily inserted into the collecting duct membrane when necessary. In hydrated individuals, less channels- less H20 recapture into the instititual fluid- increased urine volume