Defining conditions that lead to the retention of water: The importance of the arterial sodium concentration

• Published in: Kidney international Vol. 67; no. 2; pp. 613 - 621
• Main Authors: Shafiee, Mohammad A., Charest, Andre F., Cheema-Dhadli, Surinder, Glick, Daniel N., Napolova, Olga, Roozbeh, Jamshid, Semenova, Elena, Sharman, Asheer, Halperin, Mitchell L.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.02.2005; Nature Publishing; Elsevier Limited
• Subjects: Adolescent; antidiuretic hormone; Arteries - metabolism; Biological and medical sciences; Body Water - metabolism; Diuresis; Female; fructose; heat loss; Humans; integrative physiology; intestinal tract; Male; Medical sciences; Muscle, Skeletal - metabolism; Nephrology. Urinary tract diseases; Receptors, Vasopressin - analysis; Sodium - blood; Vasopressins - secretion; Veins - metabolism; water diuresis; fructose; water diuresis; heat loss; intestinal tract; antidiuretic hormone; integrative physiology; Water; Diuresis; Temperature; Nephrology; Digestive system; Gut; Loss; Environmental factor; Concentration; Retention; Artery; Fructose; Urology; Heat; Antidiuretic hormone; Sodium; Blood vessel; Physiology; Circulatory system; Mechanism of action
• ISSN: 0085-2538; 1523-1755
• DOI: 10.1111/j.1523-1755.2005.67117.x

Defining conditions that lead to the retention of water: The importance of the arterial sodium concentration. A water diuresis occurs when a large volume of water is ingested rapidly. Nevertheless, water conservation is required to provide a source of water for evaporative heat dissipation throughout the day. Therefore, the objective was to define conditions that permit the retention of ingested water. Volunteers collected urine q2h plus an overnight specimen; water loading was conducted after overnight food and water restriction; paired arterialized and venous blood samples were analyzed. When 20mL water/kg was consumed in <15 minutes, the peak urine flow rate was 11 ± 0.6mL/min. The volume of water retained after water intake stopped, and when the urine was hyperosmolar, correlated directly with the daily excretion of sodium plus potassium (r2= 0.63). The plasma sodium concentration (PNa) was 4.0 ± 0.5mmol/L lower in arterialized than paired venous blood 30 to 40 minutes after water ingestion began (P < 0.01). In preliminary studies, the smallest water load consumed in 15 minutes that would reproducibly cause a water diuresis was defined in each subject. This same acute water load was retained, however, if it contained 150-mmol/L fructose, but not glucose, or if it was consumed slowly (sipping). The arterialized PNa was not significantly lower than in paired venous samples when water was sipped. A large fall in arterialized and not venous PNa best reflected the signal to induce a water diuresis. Although a very large water load can induce a water diuresis, smaller water loads can be retained for future heat dissipation.