| pubmed-article:6811960 | pubmed:abstractText | In order to assess the effects of sodium depletion on tubular Na and H2O transport in man, renal clearance studies were performed under control conditions and after sodium depletion in 7 normal subjects. The control diet contained 250 mEq of Na daily. Sodium depletion was induced by placing subjects on a 20-mEq/day na diet and administering furosemide (40 mg) dialy for 3 days. Balance studies revealed that the subjects were in Na balance under control conditions, and that after sodium depletion had been established they were in a sodium-retaining state. Subjects were studied under both conditions, after H2O hydration and during a subsequent hypotonic mannitol infusion. After H2O hydration the minimal urinary osmolality averaged 61 and 67 mosm/kg in the sodium depletion and control states, respectively. Sodium depletion was associated with a significant reduction in C inulin, sodium clearance (CNa), urine flow (V), fractional urine flow (V/GFR), free water (CH2O), and fractional free water clearance (CH2O/GFR). During hypotonic mannitol infusion indices of absolute and fractional delivery of Na from the proximal tubule (CH2O + CNa; CH2O/GFR + CNa/GFR) were consistently reduced after sodium depletion and rose more slowly as absolute and fractional distal sodium chloride supply (CH2O + CNa; CH2O/GFR + CNa/GFR) were increased. These data are consistent with the view that modest sodium depletion in man provokes an increase in fractional sodium chloride reabsorption in both the proximal and distal tubules. | lld:pubmed |
