The ability of the kidneys to increase or decrease water absorption in the
tub*.rles is controlled Ly tne am&rnt of antidiuretic horrnone $DfN)
circr.llating in the blood. This hormone increases the permeability of the
distal tu*le and the coltecting duct to water. fu a result, m*re water can
be reabsorbed from the urine. Production of ADH is in turn r*gulated by
L*pror.*lls in the brain tlrat monitor the concentration of blood, and by
receptors in the heart that rnonitor blood volume'