Cardiovascular and renal function during total body water immersion of dogs

Abstract

Ten chloralosed dogs were studied during 2 hr of control followed by 2 hr of water immersion. Another 10 animals were studied during 4 hr of control conditions. During water immersion a significant (P< .05) diuresis occurred, due to an increase in the excretion fraction of sodium. Urea excretion and creatinine, PAH [para-amino hippuric acid] and free water clearances were not significantly altered. Respiratory rate, heart rate, and cardiac output increased significantly (P< .01). Mean arterial pressure increased 11 mm Hg (P < .06). These data indicate that the observed diuresis was due to decreased tubular reabsorption of sodium and not due to changes in ADH [antidiuretic hormone] activity. Water immersion probably augmented cardiac filling and increased end-diastolic volume, resulting in increases in cardiac out- put and mean arterial pressure. It is thought that the increased cardiac output and mean arterial pressure stimulated intra-arterial receptors which initiated decreased tubular reabsorption of sodium due to increased renal medullary blood flow and/or the action of a natriuretic hormone.