Concentration and dilution of the urine in partially hepatectomized, conscious rats.

1. The influence of partial hepatectomy on urinary concentrating ability and renal tissue sodium was determined in conscious rats deprived of water for 24 h. In comparison with a sham operation, partial hepatectomy resulted in: a) a 50% reduction in free-water reabsorption, urinary osmolality, and osmolal urine-to-plasma ratio; b) depression of free-water reabsorption at similar levels of osmolal clearance above 200 microliter/min per ml of GFR during the infusion of hypertonic NaCl and vasopressin; and c) a 30% reduction in sodium content of the renal papilla and outer medulla. 2. The renal response to an intravenous water load (2.5% glucose infused to 2.5% of body wt at 0.4 ml/min) was determined in sham-operated and partially hepatectomized, conscious rats. By 60 min after the water load, both groups had excreted practically all of the load. However, during and for 30 min after the infusion in the partially hepatectomized group, the percent of the water load excreted, urine flow, and free-water clearance were significantly reduced while urinary osmolality and osmolal urine-to-plasma ratio were significantly elevated. 3. These experiments demonstrate that shortly after partial removal of the liver the renal concentrating ability is defective and the excretion of a water load is not grossly impaired.