Abstract

Urine output may be reduced and water retained in the body for a number of reasons, many of which affect water only secondarily. For instance, any process or substance which alters the electrolyte balance will almost certainly also affect water excretion. As examples may be mentioned hepatic and adrenal disorders, and the changes in steroid balance that occur during the sexual cycle. More directly, water excretion may be diminished when the blood pressure in a part or the whole of the kidney is reduced, or where the renal vessels undergo general constriction. Such renal vascular changes may be caused by substances in the circulating blood, or by activity of the renal nerves. Finally, water excretion may be reduced by the specific action of the antidiuretic hormone of the posterior lobe of the pituitary, and also, therefore, by all substances and conditions that increase the rate of release of the hormone into the circulation. A study of the literature makes it evident that ADH is the only known tissue substance whose normal function it is to control water excretion per se, and that it does so by an action on the cells of the renal tubules.