Sodium handling in the isolated perfused kidney of the cirrhotic rat

1. In cirrhosis the kidney tends to retain salt and water abnormally. Two theories have been proposed to account for this: the 'underfilling' theory, in which sodium retention is thought to occur secondary to perceived underfilling of the circulation, and the 'overflow' theory, in which sodium retention is considered to be due to a primary renal defect. 2. Using the model of cirrhosis produced by carbon tetrachloride administration in the rat, the ability of the kidney to excrete sodium has been examined in vivo and during isolated perfusion. 3. Cirrhotic animals demonstrated a reduced ability to excrete an acute sodium load: 6 h after 2 mmol of sodium was given by gavage, 27.5 ± 10.5% had been excreted by the cirrhotic rats and 62.5 ± 7.0% by control rats (P < 0.025). 4. In contrast, during isolated perfusion, kidneys from cirrhotic animals excreted the same amount of sodium as control animals over a range of perfusion pressures from 90 to 150 mmHg (12 to 20 kPa). 5. The data are consistent with the view that in cirrhosis the kidney retains sodium in response to immediate external factors.