PRESSURE DIURESIS AND NATRIURESIS IN CIRRHOTIC RATS

Arterial hypotension in liver cirrhosis has been proposed as a major m echanism contributing to renal sodium and water retention. To evaluate kidney excretory responses at different levels of arterial pressure ( AP), we have characterized the relationships between renal perfusion p ressure (RPP) and sodium and water excretion in carbon tetrachloride c irrhotic rats. Experiments were performed in anesthetized control (n = 9) and cirrhotic rats with (Asc, n = 6) and without ascites (Cir, n = 6) by mechanically adjusting vascular resistance in animals with rena l denervation and infused with main systemic hormones. Control and Cir animals showed similar glomerular filtration rates (GFR), renal blood flows, hematocrits (Hct), and plasma proteins (PP). However, Hct, PP, and GFR were significantly lower in the Asc rats. For the same level of RPP, both cirrhotic groups excreted significantly less water and so dium than controls. Then, the pressure diuresis and natriuresis relati onships of the Cir animals were significantly depressed, but those of the Asc animals were more reduced than those of the Cir rats. These re sults indicate that the cirrhotic kidney is not able to normally incre ase the sodium and water excretion in response to changes in AP. Intra renal mechanisms, and not mainly RPP, are likely mediators of the rena l alterations of liver cirrhosis.