Relationship Between Diurnal Variations in Urinary Volume and the Excretion of Antidiuretic Substance*

In The normal individual there is a diurnal cycle of excretion of water and solids which is maximal during the daytime hours of normal activity (1–4). However, in several disease states associated with water and sodium retention, including cardiac failure and hepatic cirrhosis with ascites, this cycle of water and sodium excretion may be reversed, and maximal output is during the night (5). It was postulated that if variations in tubular activity regulate this fluctuation in water and sodium excretion, it might be possible to demonstrate appropriate variations in a controlling metabolite or hormone. Thus, during periods of antidiuresis there might be a large amount of antidiuretic substance in the urine, whereas during periods of diuresis the amount of antidiuretic substance might be relatively small. A check upon this relationship could be obtained by observing individuals with both normal and abnormal patterns of urinary excretion.