The Influence of Autonomic Vasoregulatory Reflexes on the Rate of Sodium and Water Excretion in Man

Abstract

When compared with normal persons, patients with idiopathic hypofunction of the autonomic nervous system, manifested by ortho-static hypotension, hypohidrosis, and impotence, have an enhanced ability to excrete Na and solute-free water in response to the rapid infusion of isotonic NaCl solutions. Augmented solute-free water excretion could be prevented by the administration of vasopressin. The Na excretion was not prevented by the administration of Na-retaining adrenal steroids. Enhanced Na excretion was associated with acute elevation of glomerular filtration rate (GFR) associated with extracellular fluid expansion. In addition, acute expansion of depletion of blood or extracellular fluid volume in these patients resulted in profound changes in arterial pressure, indicating a lack of ability to maintain circulatory homeostasis. The experiments suggest that the presence of well-developed autonomic vasoregulatory reflexes functioning to maintain circulatory homeostasis, may result in man''s relative inability to rapidly increase his GFR and thereby rapidly excrete excesses of salt.