RESTORATION OF WATER DIURESIS IN ADDISONIAN PATIENTS BY EXPANSION OF THE VOLUME OF EXTRACELLULAR FLUID*

Abstract

Free water clearance (Ch2O) was studied in four patients with Addison''s disease before and during both acute and sustained expansion of extracellular fluid volume (ECF). Acute expansion of ECF was produced by infusing physiologic saline immediately after an infusion of water (containing a metabolizable hexose); sustained expansion, by infusing physiologic saline for 1 to 3 days prior to an infusion of water. Both acute and sustained expansion led to marked increases in Ch2O, with values in two patients comparable to those obtained during treatment with cortisol. The rise in Ch2O was not always accompanied by rise in glomerular infiltration rate (GFR) or solute excretion. Hypotonic mannitol by vein, before and after sustained expansion, was usually less effective than water. The data suggest that free water formation does not require steroid-dependent reabsorption of sodium at distal tubular sites. It is not likely that expansion of the volume of ECF increased CH2O only by increasing GFR or the filtered load of solute. The results may indicate a relationship of some function of the volume of ECF to the release or secretion of antidiuretic hormone.